Converting annual accounts to XBRL or iXBRL is mandatory for almost all legal entities that file their annual accounts with the Dutch Chamber of Commerce (KVK), and for listed companies reporting under ESEF. Since financial year 2025, the digital filing obligation also applies to the size class large. The conversion turns an adopted set of annual accounts (PDF, Word or another source format) into a structured, machine-readable file that complies with the SBR rules of the Dutch Business Register (KVK) or with the ESEF requirements (AFM). This article explains the steps, lists common errors, and clarifies the difference between a KVK filing and an ESEF report.
Key facts
Who this applies to: all legal entities required to file digitally with the KVK (micro and small from financial year 2016, medium-sized from financial year 2017, large from financial year 2025) and listed companies on EU-regulated markets reporting under ESEF
Legal basis KVK: Article 2:394 of the Dutch Civil Code and the Decree on electronic filing with the Business Register; the report uses the Dutch Taxonomy (Nederlandse Taxonomie, NT), maintained within the SBR programme
Legal basis ESEF: Commission Delegated Regulation (EU) 2019/815, based on Article 4(7) of the Transparency Directive; in the Netherlands the AFM supervises compliance and acts as the filing mechanism
KVK format: an XBRL instance (the classic SBR format) or the European format (XHTML with embedded iXBRL tags); every size class has had this choice since financial year 2024
ESEF format: the entire annual financial report in XHTML; the IFRS consolidated financial statements are marked up with iXBRL using the ESEF taxonomy, an extension of the IFRS taxonomy
Validation: Arelle (certified by XBRL International as a Validating Processor) with the SBR Filing Rules and the KVK rules for filings; the ESEF RTS and the ESEF Reporting Manual for ESEF
Why conversion is necessary
Digital filing with the KVK was made mandatory in phases per size class: micro and small from financial year 2016, medium-sized from financial year 2017 and large from financial year 2025. With the amendment of the Decree on electronic filing with the Business Register of 18 December 2024, the last exception for large legal entities lapsed. Only issuers of listed securities remain exempt: they file their annual financial report in ESEF format with the AFM.
A PDF or Word file is not sufficient. The KVK requires a structured XBRL or iXBRL file in which every item in the balance sheet, the profit and loss account and the notes is linked to a concept from the Dutch Taxonomy. Without that link, the recipient cannot process and compare the figures automatically.
The deadlines do not change with the format: file no later than 8 days after adoption of the annual accounts, and in any case within 12 months after the end of the financial year.
See also Electronic filing: SBR or iXBRL? for the background of the obligation.
First decide: XBRL instance or iXBRL?
For a KVK filing, there has been a choice between two formats since financial year 2024. That choice determines the rest of the conversion process, so make it before step one.
Feature | XBRL instance (classic SBR) | iXBRL (European format) |
|---|---|---|
Readability | Machine-readable only; rendering requires separate software | One XHTML file: readable in the browser and machine-readable |
Layout | Fixed framework of the taxonomy, no custom layout | The entity's own presentation of the annual accounts is preserved |
Extension taxonomy | Not applicable: fixed entry points per size class | Mandatory: an own extension taxonomy, packaged with the report in a single Report Package |
Maximum size | 15 MB | 100 MB (Report Package) |
Sustainability reporting (CSRD) | Not possible | This format is mandatory |
Submission | Digipoort (SBR software) or the KVK upload portal | Digipoort (SBR software) or the KVK upload portal |
The Regulatory Technical Standard (RTS) of the SBR Business Register domain designates iXBRL as the recommended format for annual reports in which presentation plays an important role. Two practical rules: only one adopted annual report can be filed per financial year, and the auditor's report must be filed in the same format as the annual accounts.
The six steps of a correct XBRL conversion
A reliable conversion always goes through the same phases, whether it concerns a small business or a large enterprise.
Step | What happens | Point of attention |
|---|---|---|
1. Delivery of the adopted document | The accountant or preparer delivers the final PDF or DOCX | Always use the adopted version; interim drafts lead to incorrect tags |
2. Extraction of financial data | Software or a specialist extracts the balance sheet, profit and loss account and notes from the document | Tables, footnotes and merged cells require extra checking |
3. Mapping to taxonomy concepts | Each item is linked to the correct concept in the KVK taxonomy (NT) or the ESEF taxonomy (IFRS) | Incorrect mapping is the most common cause of validation errors |
4. Review by the reviewer | The accountant or internal reviewer checks the tags, the amounts, signs and scale, and the structure | The four-eyes principle is crucial; good software shows the tags next to the readable text |
5. Validation against the operative rules | The file is validated with Arelle against the SBR Filing Rules and KVK rules, or against the ESEF RTS and the ESEF Reporting Manual | Errors and warnings are reported per concept and per rule |
6. Export of the validated package | The final package (XBRL instance or iXBRL Report Package) is ready for submission to the KVK or the AFM | Keep the validation report as demonstrable evidence of the pre-filing checks |
Step 3 in detail: entry point and size class
The mapping determines the quality of the end product. The correct entry point in the KVK taxonomy depends on the size class: micro and small use a limited schema, medium-sized and large use more extensive entry points with more mandatory disclosures. For ESEF, the entry point of the ESEF taxonomy applies, and extension elements must be anchored to the base taxonomy element with the closest accounting meaning.
The size class follows from three criteria: balance sheet total, net turnover and average number of employees. A legal entity falls into a class if it meets at least two of the three criteria for two consecutive financial years. Since financial year 2024, thresholds raised by roughly 25% apply (optionally already applicable to financial year 2023):
Size class | Balance sheet total | Net turnover | Employees |
|---|---|---|---|
Micro | ≤ € 450,000 | ≤ € 900,000 | < 10 |
Small | ≤ € 7.5 million | ≤ € 15 million | < 50 |
Medium-sized | ≤ € 25 million | ≤ € 50 million | < 250 |
Large | > € 25 million | > € 50 million | ≥ 250 |
Read the size criteria for annual accounts for the full breakdown per class, including the consequences for exemptions and the statutory audit requirement.
Never use a medium-sized entry point when the entity qualifies as small, or vice versa. The entry point determines which concepts are available and which data are mandatory; validating against the wrong entry point produces errors that only become visible late in the process.
Manual vs. with software
Manual tagging in an XML editor requires deep taxonomy knowledge and is hard to repeat across the annual taxonomy updates. Conversion software takes the document as input, proposes mapping suggestions per taxonomy concept and validates automatically. The reviewer keeps full control; the software removes the repetitive work. For accounting firms with multiple clients, the difference in turnaround time is substantial, especially now that the iXBRL variant also requires an extension taxonomy and a Report Package.
KVK (SBR) versus ESEF (IFRS): two strictly separated outcomes
This distinction is fundamental and must never be mixed up.
Feature | KVK filing (SBR) | ESEF reporting |
|---|---|---|
Reporting framework | Dutch GAAP (Book 2 Title 9 of the Dutch Civil Code and the RJ guidelines), or IFRS | IFRS (consolidated financial statements) |
Taxonomy | Dutch Taxonomy with the KVK entry points | ESEF taxonomy (extension of the IFRS taxonomy, ESMA) |
Format | XBRL instance or iXBRL (XHTML), choice since financial year 2024 | XHTML; iXBRL mark-up of the IFRS consolidated financial statements |
Entity ID | KVK number | LEI (Legal Entity Identifier, ISO 17442) |
Recipient | KVK, via Digipoort or the upload portal | AFM (the officially appointed filing mechanism in the Netherlands) |
Extensions | XBRL variant: no own extensions; iXBRL variant: own extension taxonomy mandatory | Only where the base taxonomy falls short, with mandatory anchoring |
Block tagging of the notes | Not yet mandatory; follows one year after ESMA's revised block-tagging approach | Mandatory since financial year 2022 |
Target group | Almost all Dutch legal entities with a filing obligation | Listed companies on EU-regulated markets |
An issuer of listed securities files its ESEF annual financial report with the AFM and is therefore exempt from the SBR filing obligation at the KVK. If an organisation touches both frameworks, for example as a large Dutch subsidiary of a listed group, two separate tracks apply: two files, two taxonomies and two validation processes.
Common errors in the conversion
1. Wrong entry point for the size class
An employee selects the medium-sized entry point while the entity qualifies as small, or vice versa. Moreover, since the thresholds were raised as of financial year 2024, many entities have moved down a class; anyone still applying the old criteria tags against an entry point that is too heavy. The errors often only become visible in the validation step.
2. Untagged items
Not all items are captured in the first extraction round. For an iXBRL filing, the RTS requires detailed tagging of all amounts in the reported currency in the primary statements, including dashes or empty cells that represent zero, plus mandatory metadata such as the KVK number, name, legal form and size class. Missing tags produce an incomplete file that fails the minimum reporting requirements.
3. Company-only and consolidated mixed up
The taxonomy does not distinguish company-only and consolidated figures with separate concepts, but with a dimension: the same concept carries the consolidated or company-only domain member. An amount placed in the wrong scope is sometimes invisible to the validator but substantively wrong. If the annual report contains both sets of financial statements, the RTS requires at least the consolidated financial statements to be tagged.
4. Amounts at the wrong scale
If the annual accounts present amounts in thousands of euros, the document shows for example 1,234 while the actual value is € 1,234,000. In iXBRL a scale attribute handles that multiplication; if it is set incorrectly, the reported values deviate from the visible text by a factor of 1,000. In its ESEF review of the 2023 reporting year, the AFM explicitly named the direction (sign) and scale of tagged amounts as recurring points of attention.
5. Using an outdated taxonomy version
The Dutch Taxonomy and the ESEF taxonomy are updated annually. For KVK filings, a set of base taxonomies remains usable for three years; for financial year 2025, both the 2024 and the 2025 set may be used, but using the most recent set is strongly recommended. A file built against a version that is no longer supported can be rejected.
Related topics
What is iXBRL and how does it differ from XBRL? for the technical background of the two formats
Filing annual accounts digitally in iXBRL for the filing process per document type and size class
Electronic filing: SBR or iXBRL? for the choice between the two permitted formats for KVK filings
Frequently asked questions
What is the difference between XBRL and iXBRL? XBRL is a standalone, structured file that is machine-readable only. iXBRL embeds the XBRL tags in an XHTML document, so the file is readable by both people and machines. For KVK filings both formats have been permitted since financial year 2024; ESEF requires XHTML with iXBRL mark-up.
What does iXBRL stand for? iXBRL stands for Inline eXtensible Business Reporting Language. It combines a readable report with embedded, structured XBRL tags in a single XHTML file.
Can I convert a Word document or PDF directly to XBRL? Yes, using conversion software. The platform extracts the financial data, proposes mappings based on the taxonomy and generates a valid XBRL or iXBRL file. A mapping and validation step is always needed: the document does not become an XBRL file by itself.
Which taxonomy do I use for a KVK filing? The KVK taxonomy within the Dutch Taxonomy. The correct entry point depends on the size class: micro, small, medium-sized and large each have their own entry points. If you choose the iXBRL variant, an own extension taxonomy is part of the filing as well.
Is ESEF the same as a KVK filing? No. ESEF applies to listed companies that submit their annual financial report with IFRS consolidated financial statements to the AFM. KVK filing applies to almost all Dutch legal entities with a filing obligation. The two regimes use different taxonomies, rules and recipients.
When must the annual accounts be filed? No later than 8 days after adoption, and in any case within 12 months after the end of the financial year. Schedule the conversion and validation well before that deadline, so there is time to resolve validation errors.
What does validation of an XBRL file for a KVK filing check? The file is validated with a certified XBRL processor such as Arelle against the SBR Filing Rules and the KVK rules. Among other things, these check whether the correct entry point was used, whether all mandatory data are present and whether the amounts are consistent.
Doc2iXBRL for converting annual accounts
Doc2iXBRL supports accountants and internal filing teams in converting an adopted PDF or DOCX into a valid XBRL or iXBRL file. AI proposes mappings per taxonomy concept, the reviewer confirms or adjusts every tag, and Arelle validates the end result automatically. The platform covers KVK filings (Dutch GAAP, Dutch Taxonomy) and ESEF reporting (IFRS, ESEF taxonomy) as two fully separated workflows. Doc2iXBRL does not guarantee acceptance by the KVK or the AFM, but delivers a technically validated package that is ready for submission.
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KVK: Filing with SBR and the size classes: filing obligation, formats and size criteria
SBR Business Register domain: the RTS, the Reporting Manual, taxonomies and example files for electronic filing
Staatsblad 2024, 52: the implementation decree with the raised thresholds as of financial year 2024
AFM: making available and filing and ESMA on ESEF: the ESEF obligations for listed companies
XBRL International: Arelle certification: the current certification status of the validator
