How to Read and Check a VAT or GST Number by Country

A German client sends you their tax number as DE123456789 and your invoice template has a box for it. Is that right? Should it start with DE? Is nine digits enough? Get it wrong and their accounts payable team bounces the invoice, or worse, you charge VAT when a reverse charge applied. A few seconds of pattern-checking saves a week of email.

Every VAT and GST number follows a shape. Once you know the shape for the country you are billing, you can catch a typo or a wrong number on sight, before it ever reaches an AP inbox.

Start with the two-letter prefix

Inside the EU, and in the UK, a VAT number starts with a country code. DE for Germany, FR for France, NL for the Netherlands, IE for Ireland, GB for the United Kingdom. The prefix tells you where the business is registered for VAT, which is not always where they are headquartered. A Dutch holding company might invoice through a German entity with a DE number.

The prefix matters most on cross-border sales. If you are a UK supplier billing a French business with a valid FR number, the reverse-charge mechanism usually applies and you do not add VAT. No prefix, no reverse charge, and you may be on the hook for the tax. So the first thing to confirm is that the number carries the country code you expect.

Outside Europe the convention changes. Australia uses an ABN, no letters, 11 digits. India uses a GSTIN, 15 characters with no country prefix. Singapore, New Zealand, and South Africa each have their own registration number rather than a lettered VAT number. Do not expect a two-letter code everywhere.

Check the length and character mix

After the prefix, each country fixes the number of characters and whether they are digits or a mix of letters and digits. This is the fastest single check you can run.

If a client hands you a nine-digit German number with no DE in front, that is not an error on their side. Many businesses quote the number without the prefix in day-to-day use, then add it for cross-border paperwork. You add the prefix on the invoice. If a supposedly German number has ten digits, stop and ask. Something is off.

For the full country-by-country breakdown, keep the reference list of VAT and GST number formats open while you set up a new international client. It covers the prefixes, lengths, and character rules in one place.

Use the check digit to catch typos

Most of these numbers build in a check digit, a value derived from the other digits by a fixed formula. Its whole purpose is to fail when someone transposes two figures. You do not need to compute it by hand, but knowing it exists tells you why an online validator rejects a number that looks fine to the eye.

The Indian GSTIN is the clearest example of structure you can read. The first two characters are the state code. The next ten are the supplier's PAN. The thirteenth reflects the number of registrations under that PAN, the fourteenth is a fixed Z, and the last is a check character. If the fourteenth character is not Z, the number is malformed. That single glance rules out a lot of bad data.

Australia's ABN uses a weighted checksum across all eleven digits. If an ABN fails validation, treat it as unusable rather than close enough. AP systems in Australia often reject an invoice outright when the ABN does not check out.

What to do before the invoice goes out

Three quick moves catch nearly every problem. Confirm the prefix matches the country you are billing. Count the characters against the expected length. Run the number through an official validator (the EU runs VIES for member-state numbers, HMRC runs a checker for GB numbers, the ATO checks ABNs). If all three pass, put the number on the invoice exactly as validated, with the prefix.

Store the confirmed number with the client so you are not re-checking it every month. When you create the invoice, the tax number belongs in the billing entity block, which the recipient can correct on their end if it is wrong. With recipient editing on the invoice link, a client who spots a stale VAT number fixes it directly and you get notified, instead of a rejection two weeks later.

The number format is one piece of a compliant cross-border invoice. The tax treatment, the currency, and the payment details all have to line up too, which the guide to international invoicing done the practical way walks through end to end. And if you are unsure whether to charge tax at all on a given sale, that decision follows from the client's status, not just their number.

Set the format check into your routine for every new international client, and a wrong or mistyped tax number stops being the thing that quietly holds up your payment.