On 5 March 2026, the Danish Business Authority published a strategy paper setting out a fundamental change in Denmark’s approach to e-invoicing document standards. The country will phase out its longstanding national format, OIOUBL, and migrate entirely to a localised version of the Peppol BIS 4 standard — branded as NemHandel BIS 4. The strategy is currently in public consultation, open until 27 March 2026.
This is not an incremental upgrade. It is a structural decision to abandon a dual-format architecture that has been in place for nearly two decades and replace it with a single, internationally interoperable standard. For service providers, software vendors, and public authorities operating in the Danish market, the implications are significant.
Background: How Denmark Got Here
Denmark was an early mover in e-invoicing. In 2005, the government mandated electronic invoicing for all suppliers to public authorities — among the first B2G e-invoicing mandates in Europe. The national OIOUBL format, based on UBL 2.1, was introduced alongside the NemHandel infrastructure to support this requirement. By today, nearly 70,000 organisations are registered as OIOUBL invoice recipients in the NemHandel registry, and 99% of all B2G invoices are already electronic.
In parallel, Denmark played a founding role in the Peppol initiative, launched in 2008, which built on the NemHandel experience to create a pan-European e-invoicing infrastructure. The NemHandel registry itself functions as a Peppol Service Metadata Publisher (SMP), and the two ecosystems have coexisted — with OIOUBL serving domestic needs and Peppol BIS handling cross-border interoperability.
The 2022 Bookkeeping Act reinforced this dual-format approach by requiring all certified digital bookkeeping systems to support both OIOUBL and Peppol BIS. The rollout of this obligation has been phased, with the final wave of businesses (those with turnover above DKK 300,000) required to comply by January 2026.
The OIOUBL 3.0 Reversal
In November 2024, the Danish Business Authority released OIOUBL 3.0 as a release candidate — a major update intended to align the national format with EN 16931 while maintaining its richer feature set (including payment automation via NemKonto and extensive data validation). The update was designed to be a compatibility-breaking change from OIOUBL 2.1.
The market response was negative. Service providers and software vendors pushed back on the timing and complexity: launching a costly national format upgrade just as the EU’s ViDA directive was reshaping the entire European e-invoicing landscape was seen as strategically misaligned.
In January 2026, the Business Authority confirmed what the market had been asking for: OIOUBL 3.0 was formally cancelled. Instead, the authority announced it would pursue a single-format strategy. The March 2026 strategy paper now details exactly what that means.
The New Direction: NemHandel BIS 4
The strategy commits Denmark to migrating from OIOUBL to Peppol BIS 4, with national extensions. The resulting format is called NemHandel BIS 4 — the Peppol BIS 4 specification plus mandatory Danish extensions that preserve the automation and validation capabilities currently provided by OIOUBL.
Why Wait for Peppol BIS 4 (and Not Use BIS 3)
The authority is explicit about why the migration does not target the current Peppol BIS 3. Two reasons:
First, Peppol BIS 3 lacks support for several data elements that are essential for Danish public sector invoice processing — most notably, the fields required for automated payment routing via NemKonto. Migrating to BIS 3 would mean losing functionality that Danish authorities depend on.
Second, Peppol has already initiated the development of BIS 4, incorporating the new PINT (Peppol INTernational) architecture. Migrating to BIS 3 now would mean a second migration to BIS 4 within a few years — an unnecessary cost and disruption for the entire ecosystem.
The PINT Architecture: Why It Changes Everything
The PINT architecture is the critical enabler of this strategy. Under the current Peppol model, national extensions to BIS 3 are standalone document specifications that can only be exchanged if both trading partners support the same extension. This breaks interoperability — a Danish extension document cannot be read by a receiver that only supports the base BIS 3 specification.
PINT changes this by introducing a layered document structure:
- Layer 1 — PINT Core: A set of data elements common to all Peppol invoices globally.
- Layer 2 — European Norm: The EN 16931 data elements required by EU VAT rules.
- Layer 3 — Peppol BIS 4 EU: Any additional EU-wide extensions beyond the base norm.
- Layer 4 — National extensions: Country-specific data elements (e.g., Danish payment automation fields) that can be added without breaking the underlying layers.
The key innovation is that a receiver can process the layers it understands and ignore the rest. A Swedish buyer receiving a NemHandel BIS 4 invoice from a Danish supplier can process the EN 16931 core and the BIS 4 elements — even if it does not support the Danish national extension. The Danish-specific data is still present in the document but does not prevent interoperability.
This solves the problem that has kept Denmark locked into a dual-format model: the need for a rich, nationally tailored invoice alongside international interoperability. With PINT, both goals can be achieved in a single document.
Migration Timeline
The strategy sets out a phased transition aligned with the development timelines of CEN (the European standards body) and Peppol:
| Period | Milestone |
| 2026 | CEN finalises updated EN 16931; Peppol develops BIS 4 (target: end of 2026) |
| 2027 | Danish Business Authority develops NemHandel BIS 4 national extensions in collaboration with public and private stakeholders |
| Nov 2027 – May 2028 | Release candidate published; comment period |
| May – Nov 2028 | Phase-in: NemHandel BIS 4 becomes mandatory; OIOUBL 2.1 becomes optional |
| Nov 2028 – May 2029 | Phase-out: OIOUBL 2.1 support ends |
| Mid-2029 | Migration complete; single-format environment |
The timeline follows NemHandel’s standard deployment windows (15 May and 15 November). OIOUBL 2.1 will be maintained throughout the transition period — there is no gap in support.
Once the migration is complete, the Bookkeeping Act requirement for digital bookkeeping systems to support both OIOUBL and Peppol BIS will be amended. Systems will only need to support NemHandel BIS 4.
Scope and Limitations
The strategy explicitly covers only invoice-related documents: invoices, credit notes, and application responses. Other OIOUBL document types (e-orders, e-receipts, catalogues) will continue to be supported in their current form. The Business Authority has indicated that these will eventually migrate to a PINT-based architecture as well, but that requires Peppol to upgrade the corresponding specifications first — and no timeline has been set for that work.
What This Means in the Broader European Context
Denmark’s decision is significant beyond its borders because it establishes a template for how mature national e-invoicing frameworks can converge onto a single European standard without sacrificing local functionality.
The challenge that Denmark faced — a well-established national format with rich automation features that Peppol BIS could not replicate — is not unique. Other countries with strong national standards (such as Norway’s EHF, or the various national UBL adaptations across the Nordics) will face similar decisions as ViDA pushes toward EN 16931 uniformity. Denmark’s answer — wait for PINT, build national extensions on top of BIS 4, and run a structured migration — provides a concrete model.
The ViDA connection is direct. From 1 July 2030, all intra-Community B2B invoices must comply with EN 16931. By completing the NemHandel BIS 4 migration before that date, Denmark ensures that its domestic and cross-border invoicing operate on the same standard from day one — eliminating the need for format conversion between domestic and EU transactions.
