Every group finance team has that spreadsheet: Belgium went live in January, Poland in February and April, France arrives in September, Germany's issuing deadline sits at the end of the year, and somebody has just added a line for the UK.

What the spreadsheet never shows is whether those invoices can be received and validated on arrival, at volume, against your own rules, without a project per country. Checking tens of thousands of them a month against country rules, your vendor master and your open purchase orders, and returning a rejection the supplier can act on, is the actual work hidden behind the different e-invoicing formats.

The calendar, entity by entity

Italy has required electronic invoices between parties resident or established in Italy since 1 January 2019, through the Sistema di Interscambio. Belgium made structured e-invoices compulsory between taxable persons established in Belgium on 1 January 2026, with a three-month tolerance on penalties for companies that could show they had prepared in good time. That scope matters for a multi-entity group: on the administration's stated position, an entity holding a Belgian VAT number without a fixed establishment there is outside the obligation, and the law is to be amended to say so.

Poland's KSeF became mandatory for issuing on 1 February 2026 for companies with 2024 sales above PLN 200 million, and on 1 April 2026 for nearly everyone else, with the smallest issuers following on 1 January 2027. Read that second date carefully, because it's the one most groups have wrong: April deferred issuing only. Receiving through KSeF has been compulsory for every taxpayer since 1 February 2026.

France requires every business to receive e-invoices from 1 September 2026 wherever the supplier is obliged to issue one, with large and mid-sized companies issuing from that date and smaller ones from 1 September 2027. Germany has obliged every domestic business to receive since 1 January 2025, while issuers may keep sending paper, or a PDF the recipient has agreed to accept, until the end of 2026, or the end of 2027 below an 800,000 euro turnover.

The UK will introduce mandatory e-invoicing for all VAT invoices from 2029, with the roadmap due at Budget 2026. The standard is still open: many respondents pushed for Peppol, and the government's own answer is that it will review the risks and benefits of adopting an existing standard against designing a UK-specific one. And the EU's ViDA package, in force since 14 April 2025, makes digital reporting mandatory for cross-border B2B trade from 1 July 2030.

If your first date is France, it is the nearest deadline on this page.

Receiving is its own project

Issuing gets the budget, because issuing is where the penalty language points. Receiving lands on AP and gets an email.

Belgium is explicit that structured invoices travel over Peppol, that you have to be able to receive them, and that you can't register on the network yourself: it goes through an approved service provider, which the guidance calls an access point. Poland releases the invoice once the taxpayer authenticates in the national system, and there the date an invoice counts as received is the date the KSeF number is assigned. That is a VAT receipt date. Whether it also starts your contractual payment clock depends on how your terms are drafted, so have your Polish tax lead and legal confirm it for your own contracts before you rebuild a due-date rule around it. France routes through accredited platforms.

Each country adds infrastructure that somebody in your organisation has to own by name.

A PDF is no longer an invoice

In Germany an e-invoice exists only if it's issued, transmitted and received in a structured format machines can process. A plain PDF no longer qualifies; XRechnung and ZUGFeRD from version 2.0.1 do, apart from two minimal profiles. France says the same and routes B2B invoices in UBL, CII or a hybrid of structured file plus image. Belgium is blunter still: a PDF by email is no longer enough.

What arrives instead is usually a Peppol BIS Billing 3.0 document, an application of EN 16931. Factur-X and ZUGFeRD share the same idea, a PDF for people carrying XML for machines, and under the German rules the structured part prevails when the two disagree.

That last sentence has an operational consequence worth acting on this quarter. A process still extracting fields from the picture is reading a preview, not the invoice.

The five checks that belong to you

A validator tells you whether a file respects EN 16931 and its business rules, and the German ministry recommends running one. Italy's SdI returns a rejection receipt with an error code when a file fails. Neither one tells you whether the invoice is right for your business. These are yours:

• Supplier identity. Does the VAT number on the file match your vendor master, and is the bank detail the one on record?
• Commercial agreement. Is the PO still open, at these lines, at this price?
• Tax treatment. Does the tax code fit this entity and this transaction?
• Duplication. Has this invoice already arrived through another channel during the overlap?
• Returnability. When it fails, can your team send back a rejection with a reason code the supplier can act on the same day?

That fifth one is the readiness test nobody runs. A validation that only blocks moves the work into your exception queue rather than out of it.

Two kinds of invoicing, one process

The overlap between them will last years. A German supplier below the turnover threshold may send paper until the end of 2027. A Polish supplier may invoice outside KSeF, on paper or electronically, until 31 December 2026, as long as their monthly invoiced sales including VAT stay under PLN 10,000, and that cohort is obliged from 1 January 2027. And the mandates cover domestic trade, so a Dutch supplier invoicing your Belgian entity sends whatever they like.

Give structured invoices their own pipeline and you'll operate two AP processes for years. Run one flow instead: structured invoices enter as data, scans go through extraction, and both meet the same matching, coding, tax check and approval. For your team that means one queue and one set of rules, and a month-end that no longer depends on where the invoice came from. The architecture behind that single flow, from ingestion channels to EN 16931 validation and archival, has its own guide.

Country rules written as instructions, not tickets

The rules keep moving. France updated its guidance in July 2026, and Poland opened consultations on KSeF changes in June 2026, four months after go-live.

If every change becomes a development ticket, your process runs permanently one release behind the law. Keep the country rules as written instructions, in the tax lead's own words, owned by the person who answers to the local authority.

How Hypatos reads the mandated formats

With Hypatos, e-invoicing validation is a skill of the invoice processing workforce covering xRechnung, ZUGFeRD, Factur-X, FatturaPA, RO e-Factura and the KSeF structured invoice, as XML or as PDF with embedded data. The skill maps an unfamiliar schema onto your internal standard, checks structure and completeness, and renders a preview for the approver. Peppol is a network rather than a format, so a Belgian invoice reaches you over Peppol and the agent reads the file that arrives.

From there the invoice joins the same route a scanned one takes: matching, GL coding, tax compliance validation, approval, posting. Country instructions live in AI Agent Studio, so when Warsaw changes a mandatory field the Polish tax lead edits the instruction. The agents propose, a named person decides, and the record shows what was checked.

Hypatos fits when several entities are hitting different dates and you need one flow instead of a converter per country.

Which of your entities goes first

List your entities against those dates with four columns: must receive since, must issue from, how invoices reach you there, and what suppliers actually send today.

Then run one month of invoices from the entity nearest its date through the validation you intend to use, whether that's your current provider, Hypatos, or a manual check by your tax lead. How many pass, how many fail, and how many rejections your team could return the same day.

That number is your readiness, and if the failures cluster on one supplier or one field, you've found the first fix, usually in master data.

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