What to do if a VAT number is invalid

You ran a VAT lookup and the result came back invalid. Before you approve payment, apply zero-rated VAT, or close a supplier onboarding, pause and follow a clear process. Knowing what to do if a VAT number is invalid protects you from invoice fraud, input tax mistakes, and compliance problems down the line.

Step 1: Do not pay the invoice yet

The most important rule when you see an invalid VAT number on an invoice is to hold payment until the number is clarified. An invalid result from HMRC or VIES means the registration is not currently active in the official registry — it may be cancelled, never issued, mistyped, or linked to a different entity. Paying anyway leaves you with the VAT charge and the compliance risk. Read why you should verify VAT numbers before every B2B transaction for the full picture.

Step 2: Recheck the number and format

Before assuming fraud, confirm you entered the number correctly. Remove spaces and hyphens, include the country prefix — GB for the UK, IE for Ireland, DE for Germany, and so on — and run the lookup again on our free VAT checker. A simple typo is one of the most common reasons for a VAT check failed result.

UK numbers need GB plus nine digits — see check VAT number in UK. Irish numbers use IE plus seven digits and letters — see how to check a VAT number in Ireland. EU format rules are in EU VAT numbers explained.

Step 3: Contact the supplier directly

If the format is correct and the number still shows invalid, contact the supplier using details from a trusted source — not only the invoice in question. Ask them to confirm their current VAT registration number and provide an official tax document or updated invoice. Legitimate businesses can usually resolve a mismatch quickly; evasive or inconsistent answers are a red flag for a fake VAT number supplier scenario.

Step 4: Document the lookup

Keep a dated record of each check: the VAT number, the invalid result, and when you ran the lookup. This supports due diligence if a dispute or audit arises. See how VAT validation works for what official results include.

When invalid may be temporary

Occasionally VIES is unavailable or a member state database is slow to update. Wait a short time and run the check again. This applies to invalid EU VAT number lookups more often than invalid GB VAT number HMRC checks. If the result stays invalid after two attempts on different days, treat the number as not verified.

When to escalate or walk away

If the supplier cannot provide a valid number, refuses to clarify, or pressures you to pay anyway, do not proceed. Report suspected fraud to your internal compliance team or relevant authority. For high-value or recurring relationships, consider whether the partnership is worth the risk. Related guides: how to check VAT registration number and FAQ.

Run a fresh VAT check now

Whether you are dealing with a VAT number not valid result for the first time or building a standard invalid-number workflow, start with a live official lookup. Visit the Check VAT Number homepage, enter the full number with its country prefix, and get instant HMRC or VIES results — or browse more guides on our blog.