Denmark moves from OIOUBL 2.1 to NemHandel BIS 4
Denmark is preparing to phase out its national e-invoice format OIOUBL 2.1 and replace it with NemHandel BIS 4. The new format is a Danish adaptation of the international Peppol BIS 4 standard and aligns with the European semantic standard EN 16931.
The change signals a broader shift in Denmark’s e-invoicing landscape. Instead of maintaining a domestic format, the country is moving closer to the European standard model that underpins upcoming regulatory initiatives, including VAT in the Digital Age.
Background and recent developments
The Danish Business Authority confirmed this direction on 24 February 2026. The announcement follows the earlier decision to cancel the planned OIOUBL 3 standard. That already pointed to a change in Denmark’s approach to e-invoicing. In our previous update Denmark Cancels OIOUBL 3 Single e-invoicing Standard, we explained how Denmark moved away from introducing a new national format.
Over the past year the authority reviewed the future of the national framework and chose to build on existing Peppol infrastructure rather than introduce another domestic format. NemHandel BIS 4 will therefore replace OIOUBL 2.1 as the national format used within the Danish NemHandel network.
The announcement also comes shortly after several updates to the current OIOUBL framework. In early 2026 Denmark introduced validation changes to the format, covered in Denmark OIOUBL Validation Update 2026. The authorities also added sustainability related data fields, allowing companies to include CO2 information in invoices. This development is described in Denmark Adds CO2 Data to OIOUBL e-invoicing.
These developments show that OIOUBL remains active in the short term. At the same time the long term direction is now clearly focused on alignment with European standards.
Timeline and standards alignment
Current information points to a gradual transition starting in 2028 and continuing into 2029.
- 2028: Initial release of NemHandel BIS 4
- 2028 to mid 2029: Final release and implementation of NemHandel BIS 4 combined with the progressive phase out of OIOUBL 2.1
More detailed technical timelines are expected once the Danish Business Authority publishes further specifications.
NemHandel BIS 4 will be based on the Peppol BIS 4 format with adaptations for the Danish market. The new format will comply with EN 16931, the European semantic standard for electronic invoicing. This supports interoperability across EU member states and helps prepare the Danish ecosystem for upcoming VAT in the Digital Age requirements which depend on more standardised e-invoicing structures.
Impact and next steps for companies
One open question concerns the interaction with the Danish Digital Bookkeeping Act. Under current rules providers of standard digital bookkeeping systems must support the issuance and receipt of e-invoices in the OIOUBL format. It is not yet clear how these obligations will evolve once NemHandel BIS 4 becomes the national standard.
Companies currently using OIOUBL 2.1 should start monitoring the transition closely. The release candidate expected in 2028 will be an important moment to assess the technical impact and prepare systems for migration.
Changes companies need to implement include:
- Review whether ERP and e-invoicing platforms support NemHandel BIS 4
- Plan the migration away from OIOUBL 2.1
- Monitor updates related to the Digital Bookkeeping Act
- Align internal invoicing processes with the EN 16931 data model
Organisations that rely on Danish e-invoicing should follow upcoming announcements from the Danish Business Authority, as more detailed specifications and timelines are expected.
