The perfect Austrian invoice: a mandatory-elements checklist

Mandatory elements of a full invoice (UStG §11)

1. Issuer's name and address
2. Customer's name and address
3. Quantity and description of the supply
4. Date or period of supply
5. Net amount, VAT rate and VAT amount
6. Issue date
7. Sequential number — gapless!
8. Issuer's UID (and the customer's above €10,000 gross)
9. Kleinunternehmer: the exemption clause

The small-amount invoice

Below €400 gross, a simplified invoice suffices: issuer, quantity+description, date, gross amount and VAT rate. No customer data required.

Common mistakes

• Gaps in numbering — awkward audit questions.
• Missing customer UID on large B2B invoices → their input VAT is at risk.
• Editing an issued invoice — forbidden; cancel and re-issue instead.

Billtree enforces all of this: no issue without mandatory fields, gapless numbers, immutable invoices.