Denmark is undertaking the most significant change to its e-invoicing infrastructure in nearly two decades. Following a public consultation held in March 2026, the Danish Business Authority (Erhvervsstyrelsen) has confirmed its intention to retire the national OIOUBL format entirely and move to a single, unified standard based on Peppol — branded as NemHandel BIS 4. The transition is expected to be completed by mid-2029.
For a country that has long been considered one of Europe's e-invoicing pioneers, this is a structural decision, not an incremental update — and it carries real implications for any business, software vendor, or public body operating in the Danish market.
Denmark mandated electronic invoicing for B2G transactions back in 2005, making it one of the very first countries in Europe to do so. It also played a founding role in the Peppol initiative launched in 2008, which itself built on Denmark's NemHandel experience to create a pan-European e-invoicing network.
For nearly twenty years, the two ecosystems have coexisted: OIOUBL serving domestic invoicing needs, and Peppol BIS handling cross-border interoperability. The Danish Bookkeeping Act of 2022 reinforced this dual-format approach by requiring all certified digital bookkeeping systems to support both standards — a final wave of businesses with turnover above DKK 300,000 was required to comply with this requirement by January 2026.
That dual-format model has worked, but it has also created lasting complexity. Software vendors have had to build and maintain support for two separate specifications, and businesses operating across borders have faced friction reconciling Danish-specific formatting with the international Peppol ecosystem.
In November 2024, the Danish Business Authority released a draft of OIOUBL 3.0. By March 2026, that plan had been abandoned. Instead, the Authority published a strategy paper on 5 March 2026 setting out a fundamentally different direction: scrap OIOUBL altogether, and migrate fully to a Danish-localised version of Peppol BIS 4.
The public consultation that followed, running from 11 to 27 March 2026, gathered feedback from businesses, software providers, and public sector stakeholders. According to the Danish Business Authority's summary, the responses showed broad support for harmonisation and improved international interoperability — though stakeholders also flagged legitimate concerns around the cost of transition, the treatment of Danish-specific extensions, and the complexity of migrating existing systems.
The rationale behind the move is straightforward. Maintaining two parallel formats has meant higher technical debt and operational cost for every business and vendor in the Danish market. A single Peppol-based standard reduces that burden, aligns Denmark with the wider European direction set by the EU's VAT in the Digital Age (ViDA) initiative, and positions Danish businesses for the cross-border B2B e-invoicing requirements that will become mandatory across the EU from 2030.
The new standard, NemHandel BIS 4, is a localised adaptation of the international Peppol BIS 4.0 specification. It will rely on the Peppol PINT (Peppol International) framework, which is designed to support flexible national data layers while preserving cross-border compatibility — the same underlying architecture being adopted in several other jurisdictions implementing Peppol-based e-invoicing.
Other document types beyond invoices, such as purchase orders and receipts, will continue to be supported in both the old and new formats for a transitional period, giving businesses additional time to migrate those processes separately.
Infrastructure work is already underway. The Danish Business Authority released version 2.3.0 of the Nemhandel Reference Implementation on 26 March 2026, adding support for both Nemhandel and Peppol modes of document exchange and ensuring compliance with the latest Danish CIUS (v1.16.0) and Peppol BIS3 requirements. The system runs on the AS4 protocol, providing a more secure and future-proof foundation for document transfer as the migration progresses.
The migration to NemHandel BIS 4 is structured as a multi-year, phased process rather than a single cutover date:
2026 — Finalisation of the updated EU standard EN 16931 and continued development of the Peppol BIS 4 specification, alongside the Danish extensions that will define NemHandel BIS 4.
2027 onward — Development and refinement of the Danish-specific extensions to Peppol BIS 4, with continued stakeholder engagement to validate the model in practice.
By mid-2029 — Full transition complete. OIOUBL is retired, and Peppol BIS 4 becomes the single mandatory standard for e-invoicing in Denmark.
This phased approach means businesses and software vendors have a multi-year runway to plan and execute the migration, rather than facing an abrupt mandatory cutover.
For companies trading with Danish counterparties, or software providers building accounting and ERP integrations for the Danish market, this announcement is a clear signal to start planning now, even with the 2029 deadline still some years away.
Software vendors supporting Danish e-invoicing will eventually be able to retire OIOUBL-specific code paths, but should plan for an extended transition period during which both formats remain live. Businesses using Danish-built accounting systems should ask their providers directly about their NemHandel BIS 4 roadmap, particularly as the Danish extensions are finalised from 2027 onward.
More broadly, the move reinforces a pattern now visible across Europe: national e-invoicing systems are converging toward Peppol as the common backbone, driven in large part by the approaching 2030 deadline for mandatory cross-border B2B e-invoicing under ViDA. Businesses operating in multiple EU jurisdictions should treat Denmark's decision as one more data point confirming that Peppol-based architecture is becoming the default expectation across the bloc.
Denmark's decision to retire OIOUBL after nearly two decades is a notable moment in European e-invoicing — not because it introduces a wholly new concept, but because it shows one of the continent's most mature e-invoicing markets choosing simplification and international alignment over maintaining a bespoke national format. With the transition running through to mid-2029, businesses have time to prepare — but the direction of travel is now unambiguous.
Learn more about E-invoicing in Denmark.