Almost all Danish bookkeeping-obligated entities. The obligation attaches to the SYSTEM, not the invoice: keep books digitally in a registered system, store records in the cloud, and be able to send and receive e-invoices in OIOUBL and Peppol BIS. It is not a transaction-reporting mandate to the tax authority. Roughly 67,600 businesses are voluntarily registered as e-invoice recipients. The BIS 4 migration covers invoice, credit note and invoice response only — other OIOUBL documents (e-order, e-receipt) are unscheduled.
Three corrections. (1) OIOUBL 3 was CANCELLED — confirmed in Erhvervsstyrelsen's March 2026 document strategy. Anyone who built for OIOUBL 3 in 2024–25 has stranded work, and the European Commission's own country page still wrongly says OIOUBL 3.0 became mandatory in November 2025. (2) Denmark is repeatedly mis-described as having a B2B e-invoicing mandate; it does not — the duty attaches to the bookkeeping system, so the compliance question is 'is your system on the Danish register', which catches foreign ERPs out. (3) A DRAFT amendment would auto-enrol businesses into the Nemhandel register unless they opt out, but sources disagree on timing — one says default e-invoicing from July 2026, another says rules in force 1 Jul 2026 with notification by 30 Nov 2026 and auto-registration 1 Jan 2027. Unresolved; treat as draft.
4 of 6 are primary sources. Mandate dates move — treat this page as a starting point and confirm against the primary source before committing a plan.
A page is a starting point. A scoped analysis gives you the specification, the mapping and the effort — in weeks, not quarters.
