Denmark e-invoicing update: new OIOUBL validation rules and OIOUBL 3 cancelled
Denmark has announced two important developments that will shape its e-invoicing framework from 2026 onwards. New OIOUBL validation rules will become mandatory in May 2026, while the planned OIOUBL 3 standard has been cancelled. Together, these decisions confirm Denmark’s focus on data quality, interoperability, and reduced complexity for businesses.
These updates do not stand alone. They build on earlier regulatory changes, including Denmark’s digital bookkeeping requirements for 2025 and recent extensions to the OIOUBL format, such as the addition of CO2-related data fields. More background on these earlier steps is available in our overview of Denmark’s digital bookkeeping updates for 2025
and the article on CO2 data in OIOUBL e-invoicing.
New OIOUBL validation rules for May 2026
The Danish Business Authority has published OIOUBL schematron version 1.17.0.RC for OIOUBL 2.1 as a release candidate. Although labelled as a minor update, the new schematron introduces stricter VAT validations and expands the VAT code list. The main objective is to improve compatibility between OIOUBL invoices and Peppol-based e-invoicing.
This focus on structured and accurate data aligns with earlier initiatives. The digital bookkeeping rules already placed higher demands on system readiness and validation, while the introduction of CO2 data fields in OIOUBL highlighted the need for reliable, standardised information within electronic invoices.
During testing of the new schematron, a newly introduced rule, F-LIB404, was found to affect around five percent of invoices. As a result, the Danish Business Authority decided to grant an extended implementation period, giving organisations more time to adjust their invoice logic and technical setup.
The final version of the schematron is expected to be published in mid-February 2026. From that moment, companies will have until 15 May 2026 to comply. After this deadline, invoices that do not meet the updated validation rules may be rejected within the Nemhandel infrastructure.
OIOUBL 3 cancelled in favour of a single standard
In parallel, the Danish Business Authority announced on 14 January 2026 that the planned OIOUBL 3 release has been cancelled. This decision followed feedback from service providers, who highlighted the complexity and effort required to implement a new standard alongside existing Peppol requirements.
By cancelling OIOUBL 3, Denmark avoids maintaining two parallel e-invoicing standards. Instead, the country is moving toward a single standard approach, with closer alignment to Peppol. For businesses, this reduces long-term complexity, especially for organisations operating across borders or already using Peppol in other European markets.
Further clarification on this transition is expected during the Nemhandelsforum on 24 February 2026.
What this means for businesses
Taken together, these developments send a clear signal. Denmark continues to raise expectations around data quality and validation, while actively limiting unnecessary fragmentation in its e-invoicing framework.
Companies that have already adapted to Denmark’s digital bookkeeping rules and recent OIOUBL extensions, such as CO2 reporting, are generally better prepared. Others should prioritise testing and validation now to avoid disruptions as the May 2026 deadline approaches.
- Changes companies need to implement include testing OIOUBL 2.1 invoices against the new schematron version 1.17.0.RC.
- VAT logic and code usage should be reviewed to ensure compliance with stricter validation rules.
- System and process testing should be completed well ahead of the 15 May 2026 compliance deadline.
- Companies can deprioritise preparations for OIOUBL 3, as Denmark is moving toward a single, Peppol-aligned standard.
