Guide · Invoicing

How to write a compliant invoice: every mandatory field

A correct invoice must contain certain legally mandatory fields. In Germany this is governed by §14 UStG, in Austria by §11 öUStG. If fields are missing, the recipient cannot deduct input VAT — and you have to correct the invoice. This guide lists every mandatory field and explains the exception for small-amount invoices.

Mandatory invoice fields

The mandatory fields are nearly identical in Germany (§14 UStG) and Austria (§11 öUStG). Pick your country for the right legal basis and the correct small-amount threshold:

Rules for your country:
  1. Full name and full address of the supplying business and of the recipient
  2. Tax number (Steuernummer) or VAT identification number (USt-IdNr.) of the supplier
  3. Date the invoice was issued
  4. A sequential, uniquely assigned invoice number
  5. Quantity and type of goods delivered, or the scope and type of service
  6. Date of delivery or service (or of payment receipt for advance payments)
  7. The net amount broken down by tax rate, plus any reduction agreed in advance
  8. The applicable tax rate and the corresponding tax amount — or, for an exemption, a note stating it
  9. Where applicable, a note on the recipient’s retention obligation (e.g. construction services for private individuals)

Exception: small-amount invoice

In Germany, invoices up to 250 euros gross (small-amount invoice under §33 UStDV) have reduced requirements. The following suffice: the issuer’s name and address, the issue date, the quantity and type of the service, the gross amount as a single sum, and the applicable tax rate (or an exemption note). An invoice number and recipient details are not required.

Avoid common mistakes

The most common mistakes: a duplicated or missing invoice number, a missing date of supply, a sum not broken down by tax rate, and a missing tax number or VAT ID. Also check that for tax-free transactions (e.g. small-business or reverse charge) the required note is present.

Note: This guide provides general information and is not a substitute for tax or legal advice. The applicable laws govern; when in doubt, consult your tax adviser.

Frequently asked questions

Which mandatory fields must an invoice contain?
An invoice must include, among other things, the name and address of issuer and recipient, the issuer’s tax number or VAT ID, the issue date, a sequential invoice number, the quantity and type of the service, the date of supply, the net amount broken down by tax rate, and the tax rate and tax amount. The legal basis is §14 UStG in Germany and §11 öUStG in Austria.
What is a small-amount invoice (Kleinbetragsrechnung)?
A small-amount invoice is an invoice up to a total of 250 euros gross. Reduced mandatory fields apply: the issuer’s name and address, the issue date, the quantity and type of the service, the gross amount as a single sum, and the tax rate (or a note about an exemption). An invoice number and the recipient’s details are not required here.
Do I need a sequential invoice number?
Yes. Every regular invoice needs a sequential, uniquely assigned number. It does not have to be gap-free, but it must be unique — a number must not be issued twice. For small-amount invoices, the invoice number is not a mandatory field.
How long must I keep invoices?
In Germany, invoices must generally be retained for several years (typically ten years for businesses). In Austria, the general retention period is seven years. Keep both outgoing and incoming invoices in an audit-proof way.

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