Writing an invoice as a GmbH

A GmbH invoice meets two sets of rules at once: the VAT Act (§ 14 UStG) and the GmbH Act (§ 35a GmbHG). The latter is the so-called business-letter obligation and concerns all written correspondence with external effect, and thus invoices too.

Mandatory details from § 35a GmbHG:

• Full company name including the legal-form suffix “GmbH”
• Registered office of the company
• Register court and commercial register number (HRB number)
• All managing directors with first and last name
• If applicable: chairperson of the supervisory board

To this are added the UStG obligations: tax number or VAT ID, invoice number, date of supply, net/VAT/gross breakdown. On GmbH invoices all business partners are entrepreneurs, so the B2B presentation (net + VAT + gross) is standard.

On a GmbH invoice all appointed managing directors must be named, including those not active in day-to-day business. With several managing directors, stating the representation rule is sensible (but not mandatory): “authorised to represent individually” or “authorised to represent only jointly with another managing director”. The latter is also recorded in the commercial register.

Important: if a managing director changes, you must use the updated details at the latest with the next invoice. Outdated business letters are a frequent defect at shareholders' meetings and tax audits.

Legally it holds: tax number or VAT ID, one is enough. In practice, however, every GmbH has a VAT ID, if only because it usually also does EU business. Compared with the tax number, the VAT ID is publicly retrievable and better protects tax confidentiality.

In reverse-charge dealings (e.g. construction services, scrap, mobile phones, electricity trading) you must write the note “the recipient of the service is liable for the tax” on the invoice and not show VAT. Instead of the VAT, the relevant § of the UStG then appears (§ 13b).

While private clients usually pay invoices immediately, B2B invoices go through a review process. In it, three fields are almost always desired:

• Order number / purchase order number of the client, often stated in the order confirmation email
• Supplier number, if your client has listed you as a supplier
• Cost centre / project code, internal posting keys

Ask the client's purchasing department before issuing the invoice. A missing order number can delay payment by weeks, because the invoice first goes for internal clarification.

Since 1 January 2025, for domestic B2B dealings: invoice recipients must be able to receive electronic invoices in a structured format. A PDF legally no longer counts as an e-invoice, XRechnung or ZUGFeRD is required.

Transition periods:

• 2025-2026: sending classic PDF invoices still allowed (with the recipient's consent)
• 2027: obligation to send structured e-invoices for turnovers from €800,000
• 2028: obligation for all B2B turnovers

Prepare with the e-invoice generator, it creates valid XRechnung and ZUGFeRD files from the browser. Archiving in PDF/A via the PDF/A converter remains useful for classic PDFs nonetheless.