A freelancer in Germany ends up with up to four tax numbers. The Steuer-ID (11 digits, BZSt) is yours for life and never goes on an invoice. The Steuernummer (Finanzamt, changes when you move districts) or the USt-IdNr (DE plus nine digits, BZSt, free) must appear on every invoice under § 14 Abs. 4 UStG. The W-IdNr is being rolled out in stages until the fourth quarter of 2027; most freelancers already have one, quoting it is optional until then, and the Steuernummer stays in use. The mistake to stop making: writing your Steuer-ID where the invoice wants your Steuernummer.
Every new freelancer hits the same moment: a client asks for "your tax number", and three different eleven-ish-digit numbers are in the drawer. Since November 2024 there is a fourth. This piece sorts them by who issues them, when you get them, what changes over time and which one belongs on the invoice. It is shorter than the confusion suggests.
The four numbers at a glance
|
Number |
Issued by |
Format |
Changes? |
On the invoice? |
|---|---|---|---|---|
|
Steuer-ID (IdNr) |
Bundeszentralamt für Steuern |
11 digits |
Never |
No |
|
Steuernummer |
Your local Finanzamt |
10 or 11 digits by Land, 13 digits in ELSTER |
When you move to another Finanzamt's district |
Yes (or the USt-IdNr) |
|
USt-IdNr |
Bundeszentralamt für Steuern |
DE + 9 digits |
No |
Yes (or the Steuernummer) |
|
W-IdNr |
Bundeszentralamt für Steuern |
DE + 9 digits + "-00001" |
No |
Not required yet |
Steuer-ID: the one for life
The steuerliche Identifikationsnummer is, in the BZSt's words, "eine elfstellige Nummer" that "ist dauerhaft gültig und ändert sich auch nicht z. B. durch einen Umzug, eine Namensänderung oder durch die Änderung des Familienstandes". You get it as a resident, not as a freelancer. It sits on your Lohnsteuerbescheinigung from any previous job, on your tax assessments and in your tax return, and the Finanzamt uses it to find you in its system.
What it is not: a business identifier. It contains no information about your activity, and no invoice rule asks for it. You will type it into the Fragebogen zur steuerlichen Erfassung when you register, and that is where its freelance career ends.
Steuernummer: the one from the Finanzamt
The Steuernummer is issued by the Finanzamt responsible for your address after you file the Fragebogen zur steuerlichen Erfassung through ELSTER. How that registration works, and why the ELSTER certificate is the usual bottleneck, is in our guide to registering as a freelancer. There is no statutory processing time; expect weeks rather than days.
Two facts about it trip people up. First, the format varies: the Länder use 10 or 11 digits in their own patterns, and ELSTER shows the same number in a unified 13-digit form, so your Steuernummer can look different on a letter and on a screen without being a different number (Lexware). Second, it is tied to the office, not to you. Move into another Finanzamt's district and you get a new one; update your invoice template the same week.
Do not confuse it with the Steuer-ID. Different authority, different length, different lifespan. Sending an invoice with the Steuer-ID in the Steuernummer field is a § 14 UStG defect, and a client's accounting department may bounce it.
USt-IdNr: the one for cross-border work
The Umsatzsteuer-Identifikationsnummer is, per the BZSt, "eine eigenständige Nummer, die Unternehmer ... zusätzlich zur Steuernummer ihres Unternehmens vom BZSt erteilt wird". Format DE plus nine digits. Three ways to get it: tick the box in the Fragebogen (the Finanzamt forwards the request), use the BZSt online form, or write to the BZSt. The BZSt charges no fee.
You need it as soon as you invoice a business client in another EU country under the reverse-charge mechanism, or buy services from an EU supplier. Both parties' VAT IDs go on the invoice, and you check the client's in VIES, which answers valid or invalid and nothing else. The mechanism itself, including non-EU clients, is in invoicing EU and non-EU clients.
Kleinunternehmer. Holding a USt-IdNr does not end the small-business status. The BZSt issues the number to any Unternehmer under § 2 UStG, and § 19 UStG ties the status only to turnover: tax-exempt supplies below €25,000 in the prior year and €100,000 in the current year. What ends the status is crossing €100,000 or waiving it, and the waiver "bindet den Unternehmer mindestens für fünf Kalenderjahre". A Kleinunternehmer with EU clients needs the USt-IdNr for the reverse charge exactly like everyone else. Whether to keep the status is a separate decision, walked through in Kleinunternehmer or Regelbesteuerung in 2027.
W-IdNr: the new one, rolling out until 2027
The Wirtschafts-Identifikationsnummer is the business counterpart of the Steuer-ID, and the BZSt is issuing it in stages:
- From November 2024: anyone who files an annual VAT return or is a Kleinunternehmer under § 19 UStG. That is most freelancers. If you held a USt-IdNr by 30 November 2024, your W-IdNr is that number plus the suffix "-00001".
- From the fourth quarter of 2026: entities subject to corporate tax or filing joint assessment declarations.
- From the fourth quarter of 2027: the remaining economically active persons, and further suffixes ("-00002" and so on) for people running more than one activity.
Format: DE, nine digits, a hyphen and a five-digit distinguishing feature. The suffix links to the Steuernummer under which each activity is registered.
What you must do now: nothing. The BZSt states that "eine Angabe der W-IdNr in steuerlichen Erklärungsvordrucken ist bis zum Abschluss der erstmaligen Vergabe optional", and its FAQ adds: "Wenn Ihnen noch keine W-IdNr mitgeteilt worden ist, hat das für Sie keine Nachteile." The Steuernummer keeps its function and stays in use on the Länder tax forms as before. So the W-IdNr is a number to file away, not one to act on, until the rollout completes at the end of 2027.
Which number goes on the invoice: § 14 Abs. 4 UStG
§ 14 Abs. 4 Satz 1 Nr. 2 UStG requires on every invoice "die dem leistenden Unternehmer vom Finanzamt erteilte Steuernummer oder die ihm vom Bundeszentralamt für Steuern erteilte Umsatzsteuer-Identifikationsnummer". One or the other. Both is fine. The Steuer-ID is neither, and the W-IdNr is not on the list.
Many freelancers print the USt-IdNr rather than the Steuernummer on domestic invoices. It reveals less (the Steuernummer identifies your Finanzamt) and it does not change when you move. If you have one, that is the sensible default; the full field list, from sequential number to service date, is in our invoice checklist. Kleinunternehmer still need the Steuernummer or USt-IdNr on the invoice, plus a reference to the § 19 UStG exemption instead of a VAT line.
What to do on Monday
- Open your invoice template and check which number sits in the tax-number field. Eleven digits with no DE in front of it may be your Steuer-ID. Replace it with the Steuernummer or USt-IdNr.
- If you invoice or plan to invoice EU businesses and have no USt-IdNr: apply on the BZSt site today. It is free, and the reverse charge does not work without it.
- If you moved this year: confirm which Finanzamt is now responsible and whether your Steuernummer changed. Your old one on new invoices is a correction waiting to happen.
- Find your W-IdNr letter from the BZSt, or note that it is your USt-IdNr plus "-00001". Store it with the other three. Do nothing else with it until 2028.
- Run every new EU client's VAT ID through VIES before the first invoice, and keep a screenshot of the result with the invoice.
The numbers are the plumbing. The clients are the point. A free 9am profile puts you in front of companies across DACH that hire freelancers, most of whom will ask for your USt-IdNr in the first email.
This article is general information for practitioners and does not replace tax or legal advice.
