Germany already requires every domestic business to be able to receive e-invoices. That obligation has been live since 1 January 2025. The harder deadline for mid-market finance teams is issuance: from 1 January 2027, businesses with prior-year turnover above €800,000 must issue structured e-invoices in domestic B2B trade. From 2028 the issuance rule covers everyone.
If you run a finance team of two to five people on DATEV, Exact Online or Twinfield, this is not an IT project about formats. It is an operations project about inbox design, coding quality, outbound documents, approvals and GoBD-aligned archiving. The full timeline and format table live in our E-Rechnung mandate guide at /e-rechnung (also available as /e-invoice).
Receive was step one. Issue is the step that breaks PDF habits
A plain PDF or scan is not an e-invoice. Issuance means EN 16931 formats such as XRechnung or ZUGFeRD. Your suppliers already send structured files into your inbox. From 2027 your customers will expect the same from you. Teams that only fixed receipt in 2025 discover the gap when sales or order-to-cash still produce visual PDFs with no embedded XML.
ZUGFeRD is the practical B2B hybrid for many SMEs: a human-readable PDF plus machine-readable CII XML in one file. XRechnung is the structured profile you meet most often on the receive side and in B2G contexts. Cortena receives XRechnung and ZUGFeRD on payables, and issues ZUGFeRD 2.x / EN 16931 from receivables when an invoice moves to issued. Peppol send and XRechnung B2G delivery are on the near-term roadmap and available soon.
What a small finance team actually has to own
- A dedicated channel for structured invoices, not a personal mailbox that disappears when someone leaves.
- Reading XRechnung and ZUGFeRD as data on accounts payable, not OCR on a picture of a PDF.
- Issuing outgoing customer invoices as ZUGFeRD EN 16931 hybrids from receivables.
- Coding incoming lines to SKR accounts, cost centres and VAT keys before month-end.
- Approvals that clear through the month, so close does not start with a pile of exceptions.
- A GoBD-aligned trail with the original structured document linked to the posting. The archive of record stays in DATEV.
Why DATEV teams feel this first
German bookkeeping still ends in DATEV for a large share of SMEs. That is good for the Steuerberater relationship and bad for anyone who still keys invoices by hand. Structured e-invoices remove OCR guesswork, but they do not remove chart-of-accounts logic, cost-centre splits or approval policy. If the structured file lands in a shared inbox and then gets typed into DATEV, you have complied with receipt on paper and still lost the hours.
The same is true outbound. Issuing a ZUGFeRD invoice from a disconnected tool, then re-entering the same document for booking, doubles the work. The 2027 cohort needs one path: compose or receive, code, approve, hand DATEV a booking-ready batch.
A practical readiness path before January 2027
Start with a sample week of real invoices, not a workshop about standards. Measure how many arrive as PDF versus XRechnung or ZUGFeRD. Measure how long coding and chasing take. Then run the same week through a receive-and-issue path that ends in DATEV.
- Map who currently receives supplier invoices and who issues customer invoices.
- Confirm seller legal profile and buyer data quality for EN 16931 readiness on AR.
- Decide the default outbound format (ZUGFeRD hybrid for most B2B SME flows).
- Wire payables capture and receivables issue into the same approval and trail model.
- Pilot one entity first, then roll to multi-entity only after the batch quality is trusted.
Where Cortena fits
Cortena sits in front of DATEV, Exact Online or Twinfield. On AP it ingests structured e-invoices alongside PDF and paper, codes to your rules and routes approvals. On AR it issues ZUGFeRD EN 16931 when a customer invoice moves to issued. Your team reviews exceptions. Nothing posts without sign-off.
Use the short 2027 readiness page if you need a conversion checklist, and the full E-Rechnung guide at /e-rechnung (or /e-invoice) for the mandate timeline, formats and FAQ. Book a demo if you want to see a week of your invoices on both sides.