Spec cycle · May 2026

What changed in the May 2026 release

Peppol BIS Billing 3.0.21 and KoSIT xrechnung-schematron 2.6.0, diffed rule by rule from the vendored Schematron rather than read from release notes. Short answer: nothing in this cycle changes how a conformant invoice renders. What may change is whether your documents still validate.

9 October 2026

This is the first of a twice-yearly series: each May and November, within a few weeks of the release, a mechanical diff of the official validation artefacts and a plain statement of what it means for people who validate or render EN 16931 invoices. It is also late. The May release went out on docs.peppol.eu on 20 May 2026 and became mandatory on 17 August, but it was never tagged on GitHub, and our release watch was reading GitHub tags. It now reads the live artefacts. If your own tooling pins the Peppol repository by tag, it has the same blind spot; the last tag there is still v3.0.20.

Does it touch the PDF?

No. Every change in this cycle is in the validation layer: new checks, tightened checks, code-list updates, reworded messages. Our twenty-fixture corpus validated with zero fatals and zero warnings against the new artefacts without a single fixture edit, and the rendered output of every fixture is unchanged. If your invoices validated in November, their rendering is the same today. The lists below are about whether they still validate.

Peppol BIS Billing 3.0.21

Published 20 May 2026, mandatory from 17 August 2026. The headline feature is a new optional profile, billing with response (profile identifier 02), for invoices that require an invoice response message. The artefacts ship a new example for it, base-example_profile02.xml.

Six new rules, all warnings, all national

Fifteen rules whose test expression changed

These are the ones that can move a document from green to red: PEPPOL-EN16931-R004, GR-R-001-3 through -7, GR-R-002, GR-R-005, GR-R-008-3, DE-R-017, DE-R-019, DE-R-020, DE-R-026, PEPPOL-EN16931-P0100 and PEPPOL-EN16931-P0101. Two deserve a closer look.

P0100 and P0101, the invoice and credit-note type-code checks, now apply to profile 02 as well as 01. A renderer does not care which profile an invoice declares. A validation pipeline that keys on ProfileID ending in :01:1.0 now has a second value to accept.

R004, the customization-identifier check, now also rejects a value containing ::. Some access points had been sending identifiers that were malformed but technically passed the prefix test; they no longer do.

Four severity changes and a hundred rewordings

PEPPOL-COMMON-R052, PEPPOL-COMMON-R053, DK-R-003 and DK-R-017 changed flag. Roughly a hundred further rules changed only in their message text: every assertion now carries its rule identifier as a [PEPPOL-…]- prefix, matching the CEN convention, and the German, Dutch, Italian and Greek national rules were reworded in the same pass. Harmless to documents, loud in any validator log you snapshot-test.

The CEN layer inside Peppol

Peppol's artefacts bundle their own copy of the EN 16931 rules, and that copy moved too. UBL-SR-56 is new and fatal: at most one originator document reference (BT-17). BR-CO-25 is gone. That was the rule requiring a due date or payment terms whenever the amount due is positive, and it was the most argued-over rule in the standard. Its removal is the single largest loosening in this cycle.

Tests changed on BR-CO-26 (a SEPA-scheme party identifier no longer satisfies "the seller must be identifiable"), UBL-SR-23, BR-B-02, UBL-CR-674, and the currency code lists BR-CL-01, -03, -04, -05, -10, -11, -21, -25 and -26: ANG and BGN are retired, XCG is added, following ISO 4217.

KoSIT xrechnung-schematron 2.6.0

Released 31 August 2026, compatible with XRechnung 3.0, and itself built on Peppol BIS Billing 3.0.21, so the German layer and the Peppol layer finally agree on the same base.

Code lists are aligned to CEN 1.3.16, and the IBAN pattern moved into the shared common.sch. The date-format rules formalise what our CII normalizer already required, so nothing in our corpus moved.

PINT A-NZ 1.1.3

The Australia and New Zealand profile republished its artefacts on the same unversioned URL in September; the version line on the page caught up later. We pin that zip by hash, so the republish was caught and reviewed the day it happened: currency-list retirements, ibr-126 loosened for item price extensions, ibr-sr-45 removed. No corpus impact.

What we shipped

Spec cycle 2026.05: image ghcr.io/faktorei/render:2026.05, reporting spec_release 2026.05, with Peppol pinned to the commit on OpenPeppol's 2026-Q2-QA2 branch whose artefacts are byte-identical to the live files, and KoSIT pinned to v2.6.0. Corpus green, no fixture edits, rendering unchanged. A weekly check now compares the live artefacts against the pins and opens an issue on drift, so the November release, already in OpenPeppol's QA branch, will be caught the week it lands.

The pins, the vendoring script and the upstream watch are Apache-2.0: github.com/faktorei/stylesheets, under specwatch/. The rule lists above come from diffing the vendored .sch files between pins, which anyone can reproduce with pull.py at the two refs.