The verdict in three sentences
A 120-employee company invoicing from in-house software in Germany has had to accept electronic invoices since 1 January 2025 and must issue them from 1 January 2027 if its turnover exceeds EUR 800,000, and from 2028 in all cases. Connecting that software by API to an XRechnung / ZUGFeRD workflow and a Peppol access point costs, as a 2026 order of magnitude, between EUR 8,000 and 20,000 excl. VAT, plus EUR 0.10 to 0.30 per invoice, for a 6 to 10 week project. Waiting until the last quarter exposes you to overbooked integrators and rising rates.
What the rules actually require
The German Growth Opportunities Act makes structured electronic invoices the norm between domestic VAT-registered businesses. Invoices must follow the European standard EN 16931, in practice XRechnung (pure XML, UBL or CII syntax) or ZUGFeRD 2.x (a PDF with embedded XML, technically identical to the French Factur-X). An in-house tool that only produces plain PDFs no longer qualifies.
| Deadline | Obligation | Applies to |
|---|---|---|
| 1 January 2025 | Receiving e-invoices | All domestic VAT-registered businesses |
| 1 January 2025 - 2026 | Paper or plain PDF still allowed for issuing | Transition period |
| 1 January 2027 | Issuing e-invoices | Businesses with turnover above EUR 800,000 |
| 1 January 2028 | Issuing e-invoices | All businesses |
| From receipt | Archiving structured invoices | 8 to 10 year retention (GoBD) |
| Accepted formats | XRechnung, ZUGFeRD 2.x | EN 16931 core |
The options for in-house software
Three paths exist. Replacing the in-house tool with a market ERP is costly and slow. Keying invoices into a provider's web portal is only viable below 50 invoices a month. API integration keeps the existing software and automates exchanges.
| Option | 2026 upfront cost (EUR excl. VAT) | Running cost | Suitable if |
|---|---|---|---|
| Re-keying in a provider portal | 0 - 1,000 | 2 - 4 min of keying per invoice | fewer than 50 invoices a month |
| File export to a provider (SFTP) | 5,000 - 10,000 | EUR 0.10 - 0.30 per invoice | mid volumes, legacy software |
| Full API integration | 8,000 - 20,000 | EUR 0.10 - 0.30 per invoice | more than 300 invoices a month |
| Replacement with a market ERP | 40,000 - 150,000 | licences EUR 50 - 150 per user per month | full overhaul already planned |
Inside an API integration project
| Work package | Budget (EUR excl. VAT) | Duration |
|---|---|---|
| Billing data audit (VAT IDs, addresses, buyer references) | 1,500 - 3,000 | 1 - 2 weeks |
| XRechnung or ZUGFeRD generation compliant with EN 16931 | 2,500 - 6,000 | 2 - 3 weeks |
| Sending API and status tracking | 1,500 - 4,000 | 1 - 2 weeks |
| Receiving supplier invoices and accounting import | 1,500 - 4,000 | 1 - 2 weeks |
| Validation, testing and acceptance with the provider | 1,000 - 3,000 | 1 - 2 weeks |
| Total | 8,000 - 20,000 | 6 to 10 weeks |
The most underestimated point is customer data quality: missing VAT IDs, wrong buyer references, incomplete addresses. An invoice rejected by the validator blocks payment. The initial audit lets you fix the customer file before go-live.
Mini case study
Katrin, CFO of a 120-employee industrial company in Berlin, issues 1,400 invoices and receives 900 a month. API integration is quoted at EUR 14,000 excl. VAT, with a provider fee of EUR 0.20 per invoice, or EUR 460 a month for 2,300 invoices. Today, keying and matching supplier invoices takes 3 minutes each: 900 x 3 = 2,700 minutes, 45 hours a month. Automatic import removes two thirds of that, 30 hours at a loaded EUR 38, or EUR 1,140 a month. The net gain reaches EUR 680 a month from receipt alone, then more with automated issuing and fewer reminders: payback lands around 18 to 20 months, not counting the avoided compliance risk.
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FAQ
Can our in-house software stay in place?
Yes, provided it produces invoices in a structured format (XRechnung or ZUGFeRD) and sends them through a reliable channel. API integration costs, as an order of magnitude, EUR 8,000 to 20,000 excl. VAT.
When must a mid-sized company be ready?
Receiving has been mandatory since 1 January 2025. Issuing follows on 1 January 2027 above EUR 800,000 turnover, which leaves a short window to secure the flow.
How much does a provider charge per invoice?
Observed rates range from EUR 0.10 to 0.30 per invoice depending on volume, often with a monthly subscription of EUR 30 to 150. Above 2,000 invoices a month, prices are negotiable.
Why not wait until late 2026?
Integrators will be overbooked and lead times will stretch from 6-10 weeks to 3-4 months. Day rates are already rising by 10 to 20 % as deadlines approach.
Do we also need to review archiving?
Yes, structured invoices must be kept in their original XML form for 8 to 10 years under GoBD rules. Most providers offer compliant archiving for a few euros per month per thousand invoices.
Let's scope your project. Tell us your software, invoice volumes and preferred provider: we will price the API integration, give an indicative budget and a 6 to 10 week plan. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.
Mohamed Bah
Fondateur, Kolonell
Passionate about digital and entrepreneurship in Africa, Mohamed has been helping Sénégalese businesses with their digital transformation since 2020. Founder of Kolonell, he believes every SME deserves a professional and accessible online présence.
