I’m looking for a proven development partner to build an end-to-end eInvoicing module that will pass PEPPOL certification on the first submission. You must already have hands-on experience delivering PEPPOL-ready solutions and be familiar with the testing procedure, service metadata publishing, and AS4/AS2 transport profiles. Core scope • Produce a full technical blueprint, data model, and API contract. • Implement the module, wire it to our existing ERP via REST/JSON, and prepare it for on-prem or cloud deployment. • Guarantee compliance with the latest PEPPOL BIS Billing specifications, including validation artefacts and dynamic profile updates. • Deliver robust audit trails, automated retries, error handling, and role-based access. • Provide a certification support package: registration on SMP/SML, test traffic, and documentation needed for PEPPOL Authorities. Mandatory functionality • Invoice generation with UBL 2.1 and Cross-Industry Invoice (CII) support. • Validation and compliance checks against local tax requirements and PEPPOL artefacts. • Reporting and analytics dashboards covering transmission status, success rates, and exception analysis. Tech stack The underlying language and database are open for your recommendation; I’m comfortable with Java, Python, or C# for the service layer and either relational or document databases—provided the final architecture is scalable, secure, and easy to maintain. Acceptance criteria 1. Successful end-to-end test invoices exchanged in the PEPPOL network. 2. Formal approval letter from the relevant PEPPOL Authority. 3. Source code, build scripts, unit tests, and deployment guide handed over in Git. 4. Knowledge-transfer session for my internal team plus 30-day post-go-live support. If your company already holds a PEPPOL certificate or can point to a live installation, let’s talk timelines, phased milestones, and a realistic quote.