FSMA FAQs on European Single Electronic Format (ESEF) reporting and eCorporate

Rue du Congrès / Congresstraat 12-14 1000 Brussels T +32 2 220 54 08 / www.fsma.be FSMA_2021_19 of 22 December 2021 (updated 16 December 2025) FAQs on the European single electronic reporting format and eCorporate Terms and abbreviations used in this document:
 CSRD: Directive (EU) 2022/2464 of the European Parliament and of the Council of 14 December 2022 amending Regulation (EU) No 537/2014, Directive 2004/109/EC, Directive 2006/43/EC and Directive 2013/34/EU, as regards corporate sustainability reporting.  ESEF: European Single Electronic Format  ESEF Reporting Manual1 : the reporting manual published by ESMA (July 2024 version; please note that this manual is updated regularly).  ESEF Regulation: Commission Delegated Regulation (EU) 2019/815 of 17 December 2018 supplementing Directive 2004/109/EC of the European Parliament and of the Council with regard to regulatory technical standards on the specification of a single electronic reporting format.  Information RD: Royal Decree of 14 November 2007 on the obligations of issuers of financial instruments admitted to trading on a regulated market.  iXBRL (inline eXtensible Business Reporting Language): iXBRL is a development of XBRL. This is a way of incorporating machine-readable XBRL tags into an XHTML document in such a way that the document can be read by both humans and machines.  Marking up/Tagging: A process by which XBRL tags are added to financial statements.  Transparency Directive: Directive 2004/109/EC of the European Parliament and of the Council of 15 December 2004 on the harmonisation of transparency requirements in relation to information about issuers whose securities are admitted to trading on a regulated market and amending Directive 2001/34/EC.  Law of 2 August 2002: Law on the supervision of the financial sector and on financial services.  XBRL (eXtensible Business Reporting Language)is an open standard based on XML (eXtensible Markup Language) for the electronic collection and exchange of financial data. The principle underlying the XBRL language consists in identifying concepts (e.g. the heading “Revenue” in the annual financial statements) and incorporating them into a “taxonomy” (a sort of dictionary). The information presented in the annual financial statements is then marked up with the concepts from the taxonomy, so that the information can be found by a computer.  XHTML (eXtensible HyperText Markup Language) is a markup language based on XML (Extensible Markup Language). The 2025 update to the ESEF Reporting Manual has taken into consideration the 2025 proposed amendment to the ESEF Regulation, reflecting the latest update to the International Financial Reporting Standards (IFRS) taxonomy, published in 2025, as well as the latest release of the XBRL specifications. Handbook

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Table of contents

1. Scope of the ESEF ....................................................................................................................... 5
   1.1 Which companies must apply the ESEF requirements? ................................................................ 5
   1.2 Which companies do not have to apply the ESEF requirements? ................................................ 5
   1.3 Which documents must be drawn up in ESEF format? ................................................................. 5
   1.4 Do ESEF requirements apply to sustainability disclosures? .......................................................... 5
   1.5 Must universal registration documents also be drawn up in ESEF format? ................................. 5
   1.6 Must the annual financial report be presented in ESEF format for every language version in
   which it is published? ................................................................................................................................ 5
2. Other information published by the FSMA about ESEF ................................................................ 6
   2.1 Has the FSMA published other manuals or circulars about ESEF?................................................ 6
3. Contents of the annual financial report in ESEF format ................................................................ 6
   3.1 Does the marking-up (“tagging”) requirement apply only to consolidated IFRS financial
   statements or also to individual financial statements? ............................................................................ 6
   3.2 Does the marking-up (“tagging”) requirement also apply to the notes to the consolidated IFRS
   financial statements? ................................................................................................................................ 6
   3.3 Does the marking-up (“tagging”) requirement apply to sustainability disclosures? .................... 7
   3.4 Must an XBRL viewer be made available so that the XBRL markup in the annual financial report
   can also be displayed in the ESEF document? .......................................................................................... 7
   3.5 Must the ESEF annual financial report include the auditor’s report on the consolidated
   financial statements, including his or her opinion on whether the financial statements comply with
   the relevant legal requirements laid down in the ESEF Regulation? ........................................................ 7
   3.6 In what language must the labels for marking up elements of the consolidated financial
   statements be drawn up? ......................................................................................................................... 8
4. Publication of the annual financial report ................................................................................... 8
   4.1 Where must the ESEF annual financial report be published? ....................................................... 8
   4.2 Must the annual financial report also be presented in PDF format? ............................................ 8
   4.3 When must the ESEF annual financial report be published? ........................................................ 9
   4.4 Must the ESEF annual financial report be published at the same time as its PDF version? ......... 9
   4.5 Does the ESEF annual financial report have to be filed only with the FSMA and not with the
   Central Balance Sheet Office of the NBB?................................................................................................. 9
   4.6 Where can I find information about filing with the NBB? ............................................................. 9
   4.7 Where does the FSMA publish the annual financial reports? ...................................................... 9

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4.8 There is an error in the ESEF annual financial report that has been published. How can I correct
it? 10
5. Technical and practical aspects of uploading to eCorporate ....................................................... 10
5.1 Which version of the annual financial report is to be filed on eCorporate as the main
document? .............................................................................................................................................. 10
5.2 How do I upload the different language versions of my ESEF annual financial report to
eCorporate? ............................................................................................................................................ 10
5.3 May documents other than the annual financial report be uploaded to eCorporate in ESEF
format? .................................................................................................................................................... 10
5.4 In what format do I have to upload my ESEF annual financial reports? ..................................... 10
5.5 How should an ESEF file be named? ........................................................................................... 11
5.6 Should Calculations 1.1 now be used instead of Calculations 1.0? ............................................ 11
5.7 What is the maximum size of a document on eCorporate? ....................................................... 11
5.8 Does eCorporate sometimes block the uploading of reports? ................................................... 12
5.9 How can I avoid technical problems when uploading documents? ............................................ 12
5.10 Does the eCorporate software validate my ESEF annual financial report, and if so, how long
does the process take? ............................................................................................................................ 13
5.11 Where can I find the results of the validation process? ............................................................. 13
5.12 Can I test the validation of my ESEF files before officially filing an annual financial report on
eCorporate? ............................................................................................................................................ 14
5.13 How can I access the eCorporate test environment? ................................................................. 14
5.14 Is it possible to test a report several times in the test environment? ........................................ 14
5.15 How can I tell if I’m working in eCorporate’s test environment or production environment? .. 14
5.16 How must images be included in an ESEF annual financial report that contains consolidated
financial statements? .............................................................................................................................. 14
5.17 How must images be included in an ESEF annual financial report that does not contain
consolidated financial statements? ........................................................................................................ 15
6. Errors and warnings in the validation file .................................................................................. 15
6.1 What does the software validate? .............................................................................................. 15
6.2 The upload status of my file contains a severe error message (‘OAM Severe Error’): why is
that? 15
6.3 My validation file contains errors or warnings. What should I do? ............................................ 16
6.4 My validation file contains no errors or warnings. Does this mean that the ESEF file contains no
errors? 16
6.5 Can a listed company outsource the entire preparation of an ESEF annual financial report to an
external party specialized in ESEF and thereby prevent errors? ............................................................ 17

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7. What errors occur frequently in the XBRL markup? ................................................................... 17
7.1 The marked-up XBRL value contains an incorrect sign ............................................................... 17
7.2 The XBRL tag used does not match the content of the amount in the notes ............................. 18
7.3 Invisible tags or incompletely tagged financial statements ........................................................ 19
7.4 Unnecessary extension of the taxonomy with new (anchored) elements ................................. 19
7.5 Taxonomy not aligned with the update of the IFRS taxonomy .................................................. 19
7.6 Evaluation of the validation reports and impact of missing calculations ................................... 20
7.7 Layout problems in the XHTML version that lead to the figures no longer being visible ........... 20
8. Useful information and questions relating to ESEF .................................................................... 21
8.1 Where can I find useful information about ESEF? ...................................................................... 21
8.2 Where can I turn with questions that are not addressed in these FAQs? .................................. 21

Rue du Congrès / Congresstraat 12-14 1000 Brussels T +32 2 220 54 08 / www.fsma.be

1. SCOPE OF THE ESEF
   1.1 Which companies must apply the ESEF requirements?
   Companies whose securities are admitted to trading on a regulated market2 .
   1.2 Which companies do not have to apply the ESEF requirements?
   Non-listed companies (even if they own a listed subsidiary).
   Companies that list only debt securities, the denomination per unit of which is at least EUR 100,0003 .
   1.3 Which documents must be drawn up in ESEF format?
   The only document to be drawn up in ESEF is the annual financial report. This requirement does not apply to other regulated information (such as half-yearly financial reports).
   1.4 Do ESEF requirements apply to sustainability disclosures?
   Companies that are required to disclose sustainability information must include it in their management report4 . The management report is part of the annual financial report and must henceforth be presented in ESEF format.
   1.5 Must universal registration documents also be drawn up in ESEF format?
   All universal registration documents (URDs) serving as annual financial reports for purposes of the Transparency Directive must be published in ESEF format5 . Consolidated IFRS financial statements in those universal registration documents must be marked up (“tagged”) as required by the ESEF Regulation.
   1.6 Must the annual financial report be presented in ESEF format for every language version in which
   it is published?
   Language versions published on a purely voluntary basis do not have to be presented in ESEF format6 . The obligation to publish an annual financial report is laid down in Article 12 of the Information RD and Articles 3 and 4 of the ESEF Regulation.
   Article 18, §1, 2° of the Information RD.
   Article 3:6/3 of the Code of Companies and Associations.
   As a zip reporting package if consolidated IFRS financial statements are included.
   Article 20 of the Transparency Directive deals with the language in which an annual financial report must be
   prepared. The Transparency Directive provides that in some cases, the annual financial report must be prepared in multiple languages, sometimes leaving a choice between specific languages. Article 10 of the Law of 2 August 2002 transposes these requirements into Belgian law. A concrete example: a Belgian company’s shares are listed on a regulated market in Belgium and in Member State X. In accordance with Belgian law, this company prepares its annual financial report in Dutch. Imagine now that Member State X accepts annual financial reports prepared in Greek or English. The company in question must then publish its annual financial report not only in Dutch but also in English or Greek. Not only the Dutch

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In language versions published on a voluntary basis, it is best to mention that this is an unofficial version and a “translation”7 .
2. OTHER INFORMATION PUBLISHED BY THE FSMA ABOUT ESEF
2.1 Has the FSMA published other manuals or circulars about ESEF?
In its circular “eCorporate: transmission of documents” (FSMA_2013_16) and in the “eCorporate Manual” the FSMA discusses the scope of ESEF, the filing of ESEF files, the authorized formats, the validation of ESEF files and the ESEF test environment.
3. CONTENTS OF THE ANNUAL FINANCIAL REPORT IN ESEF FORMAT
3.1 Does the marking-up (“tagging”) requirement apply only to consolidated IFRS financial
statements or also to individual financial statements?
Marking up is required only for consolidated IFRS financial statements, not for individual financial statements8 . Issuers will, however, have to prepare their entire annual financial report in XHTML format.
3.2 Does the marking-up (“tagging”) requirement also apply to the notes to the consolidated IFRS
financial statements?
Yes. The notes to the consolidated IFRS financial statements must also be marked up9 . Only text blocks have to be marked up (“block tagging”) in the explanatory notes, not each and every figure. The ESEF Reporting Manual sets out how detailed the markup of the explanatory notes must be10. The manual also indicates that the explanatory notes (e.g. tables) must remain readable by humans when they are extracted to XBRL for processing11. It is worth mentioning that it is important to start in good time with preparation of the block tagging. The graph below shows what is to be tagged. language version but also the English or Greek language version (as chosen by the company for official publication in Member State X) must then be drawn up in ESEF format. ESEF Reporting Manual, guidance 1.1.
Article 4(1) of the ESEF Regulation.
Annex II(3) to the ESEF Regulation.
10 ESEF Reporting Manual, guidance 1.9. The block tagging hierarchy published on the XBRL Europe website can be useful for the implementation of the requirements explained in the ESEF Reporting Manual. 11 ESEF Reporting Manual, guidance 2.2.6.

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3.3 Does the marking-up (“tagging”) requirement apply to sustainability disclosures?
No, marking up is (at present) required only for consolidated IFRS financial statements.
3.4 Must an XBRL viewer be made available so that the XBRL markup in the annual financial report
can also be displayed in the ESEF document?
Annual financial reports must be marked up using Inline XBRL12. An XBRL viewer is needed to display XBRL tags. However, the ESEF document may not contain executable code13. Thus, no XBRL viewer may be embedded in the annual financial report. This applies to both the version on eCorporate and the one on the issuer’s website. The two versions must be identical. However, it may be useful to make an XBRL viewer available on the issuer’s website, so that the markup can be displayed. In that case, issuers should provide the necessary explanation of how to use the XBRL viewer (ESEF viewer).
3.5 Must the ESEF annual financial report include the auditor’s report on the consolidated financial
statements, including his or her opinion on whether the financial statements comply with the relevant legal requirements laid down in the ESEF Regulation? Yes. The signed report of the statutory auditor or of the person charged with auditing the financial statements is an integral part of the annual financial report14. The European Commission has confirmed 12 Article 6 of the ESEF Regulation. 13 Annex IV(14) to the ESEF Regulation. 14 Article 12, §2, 4° of the Information RD.

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3.6 In what language must the labels for marking up elements of the consolidated financial
statements be drawn up?
The labels, including those for the extension taxonomy elements used, must be in the same language as the annual financial report. ESMA recommends that taxonomy extensions also be made available in a language customary in the sphere of international finance (i.e. in English).
4. PUBLICATION OF THE ANNUAL FINANCIAL REPORT
4.1 Where must the ESEF annual financial report be published?
The annual financial report drawn up in ESEF format is the official version of that document16. Issuers are to publish17 it on their website and simultaneously to file it with the FSMA through the eCorporate platform18 . For the technical and practical aspects of uploading the annual financial report to the eCorporate platform, see section 5 of these FAQs.
4.2 Must the annual financial report also be presented in PDF format?
The FSMA recommends that listed companies also publish a PDF version of the document on their website and upload it to the eCorporate platform as an attachment to the ESEF main document19 . This will enable users to decide whether to consult the official ESEF annual financial report or to use its standard PDF version. Issuers that also present their annual financial report in a format other than ESEF must always refer explicitly to the official version of the annual financial statements in ESEF and state that the ESEF version takes precedence if there are discrepancies between the different versions20 . 15 Official Journal of the European Union, C379, 10 November 2020, p. 1, no. 2020/C 379/01. 16 Article 4 of the Transparency Directive. 17 Article 41 of the Information RD. 18 Article 42 of the Information RD. 19 To comply with the obligation to make the annual financial report available as a brochure as well (Article 36, §1, third paragraph of the Information RD). 20 This is the official version under the Transparency Directive. See also the ESEF Reporting Manual, guidance 1.0.2.

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4.3 When must the ESEF annual financial report be published?
The introduction of the ESEF format does not change the publication deadlines. Issuers are required to publish their annual financial report no later than four months after the end of each financial year21. In some cases, publication may have to take place even earlier. Issuers under Belgian law whose shares are admitted to trading on a regulated market must publish their annual financial report no later than 30 days before their annual general meeting. Other issuers under Belgian law must publish their annual financial report no later than fifteen days before their annual general meeting.
4.4 Must the ESEF annual financial report be published at the same time as its PDF version?
The FSMA expects that issuers are organized to ensure that both versions can be published at the same time22 . The publication of the annual financial report in PDF (or other formats) before publication in ESEF can be justified only for inside information considerations23 or other legal requirements24. Issuers must submit such justification to the FSMA upon request. In such cases, publication of the annual financial report in PDF must be considered to be “regulated information” and must therefore meet the requirements of regulated information (including dissemination and uploading to eCorporate25).
4.5 Does the ESEF annual financial report have to be filed only with the FSMA and not with the
Central Balance Sheet Office of the NBB?
Yes. The ESEF annual financial report must be filed with the FSMA through the eCorporate platform and not with the Central Balance Sheet Office of the NBB. For more information on the technical and practical aspects of filing the annual financial report through the eCorporate platform, see section 5 of these FAQs.
4.6 Where can I find information about filing with the NBB?
Companies must file with the NBB both their consolidated financial statements (with accompanying reports) and their individual financial statements (with accompanying reports). For more information, see the website of the Central Balance Sheet Office.
4.7 Where does the FSMA publish the annual financial reports?
The FSMA publishes the (ESEF and PDF) annual financial reports on STORI.
21 Article 12, §1 of the Information RD.
22 The ESEF version is intended to facilitate immediate access to financial information. The advantage of ESEF is lost if the annual financial report is published first in PDF and only some time later in ESEF format. 23 In particular in light of Regulation 596/2014 of the European Parliament and the Council of 16 April 2014 on market abuse. 24 ESEF Reporting Manual, guidance 1.0.2. 25 To file the ESEF version, the issuer needs to send a message to the FSMA via eCorporate.fin@fsma.be asking it to remove the original PDF file from eCorporate. The ESEF annual financial report can then be filed as the main document, with the PDF version as attachment.

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4.8 There is an error in the ESEF annual financial report that has been published. How can I correct
it?
To correct that error, please contact the FSMA via the eCorporate.fin@fsma.be mailbox. The name of the corrected version of the annual financial report must indicate that this is a subsequent version (in ESEF format or in PDF format)26. The ESEF Reporting Manual provides further details about the rules governing naming27 (see also question 5.5).
5. TECHNICAL AND PRACTICAL ASPECTS OF UPLOADING TO ECORPORATE
5.1 Which version of the annual financial report is to be filed on eCorporate as the main document?
There is no separate document line for the ESEF version of the annual financial report. Given that the ESEF annual financial report is the official version, issuers must upload the main document in this format to eCorporate. The FSMA recommends that issuers also upload a PDF version of the annual financial report to eCorporate as an attachment to the ESEF main document. For technical IT reasons, it is important to upload the (official) ESEF version(s) first, as the main document(s), and only after that the PDF (as annexes). For technical reasons it is not possible to upload the ESEF version as the main document if the PDF version has already been uploaded as the main document. If this has happened, you will have to contact the FSMA via the eCorporate.fin@fsma.be mailbox in order to delete the initial upload.
5.2 How do I upload the different language versions of my ESEF annual financial report to
eCorporate?
The different language versions of the ESEF annual financial report must be uploaded as separate files.
5.3 May documents other than the annual financial report be uploaded to eCorporate in ESEF
format?
No. Other documents, such as annual communiqués or semi-annual financial reports, may not be uploaded in ESEF format at the moment.
5.4 In what format do I have to upload my ESEF annual financial reports?
Annual financial reports that contain consolidated IFRS financial statements must be uploaded as a zip reporting package. A zip reporting package may contain maximum one report in XHTML format, in addition to the taxonomy information. If annual financial reports are prepared in several languages, each language version must be uploaded in a separate zip reporting package. It is recommended that the extension .xbri (in lower-case letters) be used for the inline XBRL reporting package, and no longer .zip, even though the reporting package is a zip file. For further information, see the ESEF Reporting Manual, guidance 2.6.1. 26 The versioning here refers to the file name (given by the issuer) and can differ from the versioning in eCorporate. 27 ESEF Reporting Manual, guidance 2.6.3.

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Annual financial reports that contain no consolidated financial statements must be uploaded as a single XHTML file and not as a zip reporting package (see also question 5.17). Several file extensions can be attached to an XHTML file. Only .HTML and .XHTML file extensions will be accepted for uploading to eCorporate. The file itself must always be in XHTML format.
5.5 How should an ESEF file be named?
Properly named files will be processed more quickly and accurately. The FSMA, like ESMA, strongly encourages entities to comply with the naming convention described in the ESEF Reporting Manual28 . The standard structure is {base}-{date}-{version}-{lang}.xbri, whereby  {base} = the LEI or the name (or an abbreviation of it) of the listed company (max. 20 characters)  {date} = the ending date of the reporting period in YYYY-MM-DD format  {version} = a digit representing the version of the submission (1 for the first submission, +1 for every subsequent resubmission)  {lang} = the language of the report (two letters, “fr” or “en” for example) This naming convention applies both to the reporting package (.xbri) and to the files it contains. For more details, see the ESEF Reporting Manual.
5.6 Should Calculations 1.1 now be used instead of Calculations 1.0?
Yes. As mentioned in the ESEF Reporting Manual29, Calculations 1.1 should now be applied. This specification notably allows for an improved handling of rounded and duplicate facts and substantially limits the possibility of receiving false error messages.
5.7 What is the maximum size of a document on eCorporate?
The maximum size of an ESEF document on eCorporate is 100 MB. This file limit applies per uploaded zip reporting package (for companies that draw up IFRS consolidated financial statements) or ESEF XHTML file (for companies that do not draw up IFRS consolidated financial statements). Since each language version must be uploaded in a separate zip reporting package or a separate XHTML file, this limit applies per language version. The 100 MB limit also applies to all PDF attachments. There is also a limit of 100 MB per upload. If the size of all the files to be uploaded exceeds 100 MB, the files must be uploaded one after the other via ‘add language’ or ‘add attachment to the current version’. For any uploading problems, please contact the FSMA via eCorporate@fsma.be. 28 ESEF Reporting Manual, guidance 2.6.3. 29 ESEF Reporting Manual, guidance 3.4.1.

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5.8 Does eCorporate sometimes block the uploading of reports?
Files that are too large or contain active content (or viruses) are blocked at the level of the eCorporate infrastructure. For any uploading problems, please contact the FSMA via eCorporate@fsma.be.
5.9 How can I avoid technical problems when uploading documents?
To avoid problems when publishing the documents, the FSMA recommends that you test the uploading of the ESEF version beforehand in the eCorporate test environment. In what follows, we provide a few tips that can help in the event of technical problems when uploading:
 Uploading is best done from a local drive. If the files are located elsewhere (e.g. in the cloud, etc.), restricted access may apply to the files to be uploaded.  In case of firewall problems or other blocks, please contact your IT manager to check the security settings (e.g. to temporarily include the URL in the list of trusted sites).  For a secure login to eCorporate, it is best to start with a cleaned internet browser (Microsoft Edge, Google Chrome, etc.). Therefore complete the following steps:
o delete the browser data (browsing history); o delete the download history; o clear the cookies and other temporary internet files; o empty the cache internet memory. After having done so, you will need to restart your browser. It is advisable to do so in private/incognito mode. We suggest that you do not open any other sessions when you are going to upload. It may also be useful to completely reboot your computer. If you have followed the above steps but the problems have not been resolved, please contact the FSMA via eCorporate@fsma.be. Please provide the FSMA with the following information:
 a description of the problem (including any error messages you receive);  your external IP address (through, for example, the following external website you can look up your external IP address: https://www.whatismyip.com/);  name and size of the uploaded file(s);  time of upload. Ensure in that case that the ESEF version has been published on the company’s website and disseminated via the other customary channels. If you are unable to upload the ESEF version on eCorporate but you can upload the PDF version, you may already upload the latter.

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5.10 Does the eCorporate software validate my ESEF annual financial report, and if so, how long does
the process take?
The eCorporate software performs a number of technical checks on the uploaded ESEF annual financial reports. The validation of the ESEF files takes place in the background once you have uploaded a document. After uploading one or more ESEF files, users of eCorporate are returned to the main screen while the validation process runs in the background. Your upload status changes to ‘Received/ESEFValidationRunning’ until the validation of your ESEF file(s) is completed. You need to refresh the main screen (via the F5 key) in order to follow the processing status of your uploaded files. Depending on the size and number of files, the validation process may take a while (sometimes up to 5 or 10 minutes). Don’t click the refresh key immediately or repeatedly, because that may disrupt the validation process. During the validation process, you cannot upload any other files. You need to wait until the current validation process is completed before you can upload a new file via ‘+ add language’ or ‘add attachment to the current version’. Once the validation process is completed and the upload was successful, the upload status will change to “Received/Validated/ESEFNoError”. Please see section 6 of these FAQs regarding error messages.
5.11 Where can I find the results of the validation process?
The FSMA makes the results of the validation process available in a validation file. You can find the validation file on eCorporate. For more information about the validation process, see section 6 of these FAQs.

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5.12 Can I test the validation of my ESEF files before officially filing an annual financial report on
eCorporate?
An ESEF test environment has been made available temporarily by the FSMA to enable filers of ESEF annual financial reports to find out in advance - without automatic publication on STORI - what validation results they would receive following a filing on eCorporate. However, the official filing of an annual financial report with the FSMA must occur through the eCorporate environment. Uploading the document in the test environment does not suffice.
5.13 How can I access the eCorporate test environment?
Access to the eCorporate test environment is the same as to the production environment. The test environment is accessible via https://ecorporate-test.fsma.be. The person responsible for eCorporate designated by the company (the ‘company administrator’) may grant access to the test environment to other employees or third parties acting for the company. Users must possess a valid certificate. For more details, see Circular FSMA_2013_16 on the FSMA’s website.
5.14 Is it possible to test a report several times in the test environment?
Yes. However, before testing a new version, the previous filing in the test environment must be rejected. Only the FSMA can do this. You should send a request to eCorporate@fsma.be if you wish to do so. The rejected document will be marked “rejected”, but it remains visible in the test environment.
5.15 How can I tell if I’m working in eCorporate’s test environment or production environment?
eCorporate’s test environment and the production environment look exactly the same. The URL (in the address bar of your browser) of the test environment does, however, differ from that of the production environment:
 URL test environment: https://ecorporate-test.fsma.be;  URL production environment: https://ecorporate.fsma.be. It is important, therefore, to check that you have logged in to the right environment. This is because documents uploaded in the test environment are not published on STORI. Documents uploaded in the production environment are published automatically and immediately on STORI.
5.16 How must images be included in an ESEF annual financial report that contains consolidated
financial statements?
When an annual financial report contains (marked-up) consolidated financial statements, images must either be embedded in the XHTML file in the zip reporting package or be included as separate files in the zip reporting package. For further information, see the ESEF Reporting Manual, guidance 2.5.1. The way in which images are included has an impact on the information appearing on STORI. When images are embedded in the XHTML file, that file is posted separately (and directly accessible) on STORI to facilitate users’ access to the annual financial report via a browser.

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When images are included as separate files in the reporting package, no stand-alone and directly accessible XHTML file is placed on STORI as this would require the FSMA to generate this file itself. Therefore, the FSMA insists on its recommendation that the annual financial report also be made available as a PDF file (see question 4.2).
5.17 How must images be included in an ESEF annual financial report that does not contain
consolidated financial statements?
An annual financial report that does not contain consolidated financial statements only needs to be in XHTML format. Such a file must be published as a stand-alone XHTML file (including images if any). Taking into account the limited size of these files in practice, the FSMA takes the view that it is not necessary to provide for the possibility of including images as separate files in a zip reporting package.
6. ERRORS AND WARNINGS IN THE VALIDATION FILE
6.1 What does the software validate?
The software checks the following aspects:
 that the reports are in the correct format (.xhtml, .xbri or .zip):
 that the various language versions of the reports are in separate files;  the file size (maximum 100 MB per file);  the accuracy of the form and the content of the reports. The checks carried out are the ones described in the following documents that ESMA makes available on its website30:
 the ESEF Reporting Manual;
 the ESEF Validation Rules Excel file;
 as regards annual financial reports that do not contain any consolidated IFRS financial statements, a limited validation is conducted in line with what is set out in the ESEF Reporting Manual in the
chapter “Guidance for preparers of ESEF reports not subject to tagging obligations”.
6.2 The upload status of my file contains a severe error message (‘OAM Severe Error’): why is that?
This error message indicates that the eCorporate software was unable to carry out the technical validations of your file. The most common causes of this are:

• The zip reporting package contains no (or an incomplete) taxonomy.
• The zip reporting package contains inadmissible documents (e.g. extra Excel, PDF or zip files).
• The zip reporting package has an incorrect file structure (see guidance 3.1.3 of the ESEF Reporting
  Manual).
  In the case of such error messages, eCorporate (usually) generates a JSON file in annex to your documents. This file contains more technical details of the potential source of the error. 30 For technical reasons, some of the checks described might not be executed.

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For questions about the cause of the error message, please contact our IT service via eCorporate@fsma.be.
6.3 My validation file contains errors or warnings. What should I do?
Most software used to prepare ESEF annual financial reports carries out a number of standard verifications in order to determine whether the report contains certain (potential) errors. Sometimes the software points to an error message. In other cases, it issues a warning. To ensure that at the time of the official filing of your ESEF annual financial report on eCorporate, the validation file does not indicate any real problems, it is advisable first to upload the annual financial report on the test platform. The problems identified in the validation file are often very technical in nature, and therefore it is best to call upon the assistance of a specialist. If the software indicates that there is an error, this must almost always be corrected. A warning is an explicit invitation to verify whether there may be a problem with the report. A warning does not necessarily mean, however, that there is an error in the report. Thus, the software may issue a warning if the “Statement of change in the name of the reporting entity” element is not filled in31. If the name of the entity has not changed, then this information is normally not present in the annual financial report and so it does not have to be marked up. A warning may also point to an error in the underlying annual financial report. This may be the case, for example, if the sum of a number of line items does not match the corresponding total. It may also be the case if there are several amounts mentioned for the same line item at different spots in the annual financial report (inconsistent duplicates32) or if information that is required by IFRS is lacking and is therefore not marked up33. The ESEF software can thus help to detect errors in the underlying annual financial report.
6.4 My validation file contains no errors or warnings. Does this mean that the ESEF file contains no
errors?
No. Not all the information can be validated by the software (or via the calculations made by the software). The technical checks carried out by the validation software are basic checks. This does not mean that no other (material) problems can arise during markup. The software checks certainly have to be supplemented by a detailed technical review of the marked-up data. There are also technological limitations: for example, the calculation rules cannot all be verified as long as there are still (consistent) duplicates in the file. Moreover, the software can only validate, for example, whether or not text has been filled in in the mandatory fields. The content of such texts, and whether or not they are in line with the standards, still has to be checked manually. If, for example, the description 31 Information that must be given in the annual financial statements under IAS 1.51, a) if the name of the entity has in fact been changed. 32 It is recommended that duplicates be rounded up or down consistently throughout the annual financial report. The ESEF Reporting Manual also requires that issuers not report inconsistent duplicates in an inline XBRL document (§ 2.2.4). 33 Thus, IAS 1.138, b) requires a description of the nature of the entity’s operations and its principal activities, and this information also must be marked up.

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/ FSMA of the company’s activities contains N/A, there will be no error message, even though that does not fulfil the requirement. See also section 7 of these FAQs, ‘What errors occur frequently in the XBRL markup?’
6.5 Can a listed company outsource the entire preparation of an ESEF annual financial report to an
external party specialized in ESEF and thereby prevent errors?
Involving external specialists in preparing an ESEF annual financial report is certainly a good idea, especially if the company lacks or has only insufficient specialized knowledge. Outsourcing does not absolve the listed company of its responsibility to fulfil ESEF requirements. Preparations for presenting the accounts in a way that corresponds to the available taxonomy and the decision to use specific extensions are aspects that cannot be entirely outsourced. This aspect requires a thoroughgoing knowledge of the information being reported and a decision-making process in order to make the right choices.
7. WHAT ERRORS OCCUR FREQUENTLY IN THE XBRL MARKUP?
The XBRL markup (tagging) of the consolidated IFRS financial statements must take into account the ESEF Regulation (including the accompanying taxonomy) and the regulatory technical standards set out therein. One of the objectives of implementing this electronic markup is to make data available in a comparable format so that they can easily be processed by stakeholders of listed companies. In order to help issuers with practical implementation, ESMA has drawn up an ESEF Reporting Manual that is regularly updated. The ESEF Reporting Manual contains both the fundamental principles and the explanations of more detailed/technical rules that are then implemented by software developers in their validations. In what follows, we set out a number of frequently occurring errors that the FSMA has observed to date.
7.1 The marked-up XBRL value contains an incorrect sign
The interpretation of a given value can often be deduced from the context of the annual financial report or from the explanatory notes. Once the XBRL data have been entered into a database, this context is often lost. An error in the sign for the marked-up values can have important consequences for users and the analyses or calculations they carry out. In the schema of the core taxonomy to mark up IFRS consolidated financial statements34, the attributes of the elements of the statement of financial position, the statement of profit or loss and other comprehensive income, the statement of changes in equity and the statement of cash flows usually indicate whether it is a debit or a credit item. The software validation rules work on the basis of the presumption that most XBRL values must be positive. The validation rules thus draw attention to (unexpected) negative signs. It is also possible that a 34 Annex VI to the ESEF Regulation.

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/ FSMA positive value was entered when it should have been negative. At the moment, there is no direct warning for this. An additional manual check of the signs is therefore important. To avoid errors in the signs in the XBRL tagging, the sign must be validated based on whether each item is a debit or a credit (and not on the basis of the presentation in the annual financial statements). In addition to a detailed manual check, a maximum number of automatic calculations and other validation checks can also help prevent errors. See also point 7.6 below, which again emphasizes adding automatic calculations. For a few examples, we refer here to the XBRL website.
7.2 The XBRL tag used does not match the content of the amount in the notes
The review that has been conducted shows that the accounts often contain items that have been marked with tags that are either too specific or too general (too broad), and therefore the content of the XBRL tag as defined in the core taxonomy35 does not match the actual content of the item in the annual financial statements. In practice, the label of the XBRL tag as included in the core taxonomy of the ESEF Regulation sometimes offers insufficient information to determine whether this label/tag is suitable for a given item in the annual financial statements. Just because the label of the XBRL tag matches the name used in the annual financial statements does not guarantee that the right tag has been used. The documentation label of a tag, found in the core taxonomy, contains the detailed description of the contents of the tag and sometimes additional restrictions that are not (clearly) indicated by the label itself. The core taxonomy also includes references to IFRS. This can also help to understand the intended content of a given tag. A practical example of this is the item ‘other reserves’, which, according to the documentation label in the taxonomy, may not contain any retained earnings. Many companies have an item named ‘other reserves’ on their statement of financial position that does not match the definition provided in the core taxonomy because they include retained earnings (and possibly other items) under this heading. The core taxonomy has a separate tag for “retained earnings”. Another frequently erroneous label use appears with the element ‘increase (decrease) in cash and cash equivalents’ that is presented in the cash flow table. Although this label often matches the description of the item in the annual financial statements, it cannot be used where the effect of changes in exchange rates on cash and cash equivalents are not included36. The core taxonomy does, after all, provide a specific label for movements, excluding the effects of changes in exchange rates, namely: ‘Increase (decrease) in cash and cash equivalents before effect of exchange rate changes’. Please note that this label (and the documentation label) were updated in the 2020 version of the taxonomy (IFRS taxonomy update 4 – March 2021, see paragraph 118) in order to make this distinction clearer. 35 Annex VI to the ESEF Regulation. 36 In that case, it can be used only for the total changes in cash and cash equivalents including the effect of changes in exchange rates.

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In addition to the label of the XBRL tag, the documentation label and the labels for other comparable elements must also be checked to make sure that the content of the element used corresponds to the content of the tagged items in the financial statements. The illustrated taxonomy, published by IFRS.org, is a handy resource for choosing the right element from the core taxonomy.
7.3 Invisible tags or incompletely tagged financial statements
Certain attributes (e.g. ‘display:none’) make XBRL tags invisible in an XHTML viewer. To get around this, it is advisable to carry out a visual check of the XHTML version of the annual financial statements in order to determine whether all tags are visible in the viewer. It can also be useful to carry out this check with software (including freely available) other than the one with which the annual financial report was prepared. We wish to emphasize that all figures in a given currency in the primary financial statements must always be (visibly) tagged. This is also true, for example, of the profit per share, information that is included as
part of a footnote, reconciliations, etc., that are displayed in the primary financial statements.
7.4 Unnecessary extension of the taxonomy with new (anchored) elements
We have noticed that superfluous taxonomy extensions are often created for elements that already exist in the core taxonomy (whether or not intended as a dimension or as a separate line). The ifrs.org website provides tools (IFRS Taxonomy Illustrated Guide) to help navigate the taxonomy. It can also be useful to consult the tagging used by other companies in order to keep to a minimum the number of extensions of the taxonomy.
7.5 Taxonomy not aligned with the update of the IFRS taxonomy
Please note that the IFRS taxonomy is regularly updated37. The taxonomy may be adjusted to new or amended IFRS standards, with elements that come up frequently in practice, in the course of general improvements and/or because of technical updates. Sometimes, only the name of a taxonomy element is changed. The taxonomy is updated by way of amending regulations38 to the ESEF Regulation. These amending regulations also specify whether, for a given year, several taxonomies are available to choose from (for instance, the previous year’s taxonomy or the new one). It is therefore important to check each year whether the correct taxonomy is being used, whether the name is still correct, and whether each extension is still needed. 37 Early information on this can be found in the IFRS Taxonomy updates released by the IFRS Foundation. Once endorsed at EU level, updates are incorporated into EU law. 38 The amendments are published in the various European languages in the Official Journal of the European Union.

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7.6 Evaluation of the validation reports and impact of missing calculations
Each result of the validation checks needs to be evaluated on a case-by-case basis to determine whether or not there is an error (see also section 6). Of course, the validation reports can work well only if, in addition to the preprogrammed checks, sufficient arithmetical relationships are also included in the automatic calculation rules39. The arithmetical relationships must also take into account the new linked (anchored) elements that were added to the core taxonomy.
7.7 Layout problems in the XHTML version that lead to the figures no longer being visible
The official version of the annual financial report is the ESEF version (i.e. XHTML document). We recommend that a visual check always be carried out of the layout of the XHTML document (and not only of the PDF version), in order to verify that tables are legible and are not crowded out by photos. This is also true for companies that are not required to include consolidated financial statements in their annual financial report, but that do have to publish their annual financial report in XHTML. When converting between file formats (e.g. from PDF to XHTML), changes may occur in the layout. 39 Annex IV(6) of the ESEF Regulation.

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8. USEFUL INFORMATION AND QUESTIONS RELATING TO ESEF
8.1 Where can I find useful information about ESEF?40

• The ESEF Regulation
• Commission Interpretative Communication of 10 November 2020 on the preparation, audit and
  publication of the financial statements included in the annual financial reports drawn up in accordance with ESEF.
• Q&A of 29 May 2019 published by the European Commission.
• The ESEF Reporting Manual41 published by ESMA (July 2024 version; note that this manual and the
  accompanying validation rules are regularly updated) and the overview of the validation rules.
• Educational material published by ESMA.
• Circular FSMA_2013_16 of the FSMA on the transmission of documents via eCorporate and the
  eCorporate Manual.
• IFRS Foundation and the IFRS Taxonomy; see also the documents on updates to the taxonomy in IFRS
  Taxonomy updates.
• The IFRS Foundation’s IFRS Taxonomy Preparer’s Guide provides pointers on topics such as how to find
  the right tag, when to create extensions and when to report positive or negative values.
• Accountancy Europe has a webpage with Collected Guidance on ESEF reporting and assurance.
• On the website of XBRL International there is a list of articles on common errors and pitfalls in ESEF
  filings.
• Filings.xbrl.org provides a substantial list of ESEF filings from different countries, including a viewer
  that allows XBRL tags to be seen, the zip reporting package, a file with validation results and a JSON file.
• List of ESEF tools provided by XBRL Europe. The block tagging hierarchy published on the XBRL Europe
  website can be useful for the implementation of the block tagging requirements explained in the ESEF Reporting Manual.
• List of XBRL-certified software provided by XBRL international.
  8.2 Where can I turn with questions that are not addressed in these FAQs?
   For technical IT questions, please use the eCorporate@fsma.be mailbox. These can include questions relating to:
• the test environment (e.g. rejection of previous test filings);
• the ESEF software on the FSMA platform, technical standards;
• the technical aspects of eCorporate;
• the technical aspects of the ESEF validation files;
• technical problems with access profiles (see section 5.2.1 of the eCorporate Manual);
• uploading problems (see section 5.2.2 of the eCorporate Manual).
  40 This list has been carefully put together, with hyperlinks, but consists for the most part of documents drawn up by third parties. Third parties may change the available information as well as the place where they make the information available, as a result of which it is possible that hyperlinks no longer work or information is no longer available or up to date. The same problem can arise with links elsewhere in this document. 41 The 2025 update of the ESEF Reporting Manual already takes into account the amendment to the ESEF Regulation proposed in 2025, in particular the latest update of the International Financial Reporting Standards (IFRS) taxonomy published in 2025, as well as the latest updates to the XBRL specifications.

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 For questions about ESEF other than technical IT ones, please use the mailbox eCorporate.fin@fsma.be. These can include questions relating to:

• the creation of new access profiles in eCorporate;
• the application of the ESEF Regulation; and
• the correction of errors in an official uploaded document (in the eCorporate production
  environment).
  Users of ESEF annual financial reports may also use the above mailboxes for their questions on the use of ESEF.