Germany USt-IdNr. validator

Germany’s USt-IdNr. (Umsatzsteuer-Identifikationsnummer) is the VAT identification number the Bundeszentralamt für Steuern (BZSt) issues to businesses for intra-EU trade — “DE” followed by exactly 9 digits, for example DE123456789. Any German business invoicing VAT-registered customers elsewhere in the EU, or listed on a VIES cross-border transaction, needs one, and it’s a different number from their domestic Steuernummer.

That distinction trips up a lot of people: the USt-IdNr. and the Steuernummer are issued by different authorities in different formats, and using the wrong one on an invoice is one of the most common German VAT mistakes — one that’s easy to catch before submission if you know what to check.

How this validator works

This tool checks the “DE” prefix, confirms the number is exactly 9 digits, and then runs Germany’s official check-digit algorithm — ISO 7064 MOD 11,10 — over all 9 digits, entirely client-side, with no signup and nothing sent to a server. A pass confirms the number is both the right shape and mathematically checksum-valid.

What a pass doesn’t tell you

As with every country in this family, though, a checksum pass never confirms the number is currently active. For that, use the BZSt’s qualified confirmation service or the EU’s VIES lookup, linked below. One more marker worth knowing: a USt-IdNr. never carries letters after “DE” and is always 9 digits — if a number has hyphens, spaces, or a different digit count, it’s likely a Steuernummer, not a USt-IdNr., and needs a different check entirely.

Scope: this page and tool cover USt-IdNr. format and check-digit validation only — not VAT registration, Steuererklärung filing, or intra-EU reporting obligations, none of which a client-side check can tell you. Use this validator to catch a typo before it reaches an invoice; use the BZSt or VIES to confirm the number is a live registration.

Content last reviewed 2026-07-07.