For tax advisory and bookkeeping firms
invowerk checks your clients' e-invoices for format and business rules. Every check produces a validation report to keep.
What the BStBK recommends
The German Federal Chamber of Tax Advisors (BStBK) recommends agreeing in the engagement who does the technical check (FAQ E-Rechnung, as of Mar 3, 2026, no. 3.1). As an example, it names the KoSIT validator, the validation program of the Coordination Office for IT Standards (KoSIT).
A business that exercises due commercial care may rely on the technical result of a suitable validation application. According to the BStBK, keeping the validation report is advisable (no. 3.3).
What invowerk checks
- XRechnung with the KoSIT validator.
- ZUGFeRD and Factur-X under the FeRD validation rules, plus the PDF against PDF/A.
- For every message, an explanation and a text for the invoice issuer.
invowerk checks the technical format, not the service, the amounts or the tax rate. No tax advice.
Batch check
Check many invoices at once, as a ZIP or several files. The batch check is included in the Essential and Scale plans (pricing).
The validation report as a record
The validation report records the checksum (SHA-256), the time, the rule sets and the result, as PDF or JSON. Keep it together with the invoice.
Data
Invoices are checked in memory and not stored. The servers are in Germany. Accept the data processing agreement (DPA) and the agreement under § 62a StBerG online.
Partner program for firms
Your firm gets its own code. With it, your clients use the first month for free. For every 3 paying clients, your firm gets one month of Essential.
A client counts once it has paid a monthly invoice after the free month. Questions of professional law about accepting the benefit are for your firm to clarify.
Code and questions: contact@invowerk.dev