UK UTR validator — check HMRC Unique Taxpayer References offline

What a UTR actually is

A UTR (Unique Taxpayer Reference)is the 10-digit number HMRC issues to every person and company on its tax records. If you're registered for Self Assessment, you have one. If you've incorporated a company in the UK, the company has one. HMRC prints it on the front page of any Self Assessment notice to file, on payment reminders, and inside the personal tax account.

The format is simple — exactly 10 digits, no letters, no separators. HMRC sometimes prints it as a 5-5 split ("12345 67890"), but it's also valid as a single run of 10 digits. There's no country prefix, no internal structure, no version marker — just ten digits.

The K suffix you might see on a payslip

When HMRC ask you to make a payment, they often quote your UTR with a letter K on the end, e.g. 1234567890K. The K is a payment reference suffix, not part of the UTR itself — it tells HMRC's payment-allocation system that this is a Corporation Tax payment for the most recent accounting period. For a Self Assessment payment, you'll usually see the UTR followed by K too. This tool accepts either form and strips the K when displaying the canonical 10-digit value.

Look-alikes — what people paste in by mistake

Half the value of this tool is telling you that you've pasted something that isn't a UTR at all. Here are the four UK identifiers most often confused with each other:

• UTR — 10 digits. HMRC. Self Assessment and Corporation Tax.
• NINO (National Insurance Number) — 9 characters. Format AA 12 34 56 C: two letters, six digits, a suffix letter (A/B/C/D). Issued by DWP and HMRC for National Insurance contributions and Income Tax PAYE coding.
• VAT registration number — 9 digits. Often prefixed GB. Issued by HMRC when a business registers for VAT.
• Companies House company number — 8 digits (England & Wales), or 2-letter jurisdictional prefix + 6 digits (SC###### for Scotland, NI###### for Northern Ireland, OC###### for LLPs, etc). Issued at incorporation by Companies House — not HMRC.

When you paste any of these, this tool detects them by shape and tells you what they probably are, instead of just barking "wrong length". That alone catches a huge fraction of real-world mis-tax-reference errors.

The advisory mod-11 check digit

HMRC's internal systems use a modulus-11 check digit to catch typos before they propagate. The widely-cited algorithm: multiply digits 2 through 10 by the weights 6, 7, 8, 9, 10, 5, 4, 3, 2, sum the products, take the remainder modulo 11, and the leading digit should equal (11 − remainder) mod 11.

The catch: HMRC does not officially publish this algorithm. It's the version that's found its way into Xero, FreeAgent, Sage, and most open-source tax libraries, and it appears to hold on the UTRs we've inspected — but we can't guarantee it's exhaustively correct. That's why we surface the mod-11 result as advisory: a passing check is a strong signal you've typed it right, a failing check is "probably a typo — double-check on HMRC", but we never block on it. The format check (exactly 10 digits, not all zeros) is the definitive verdict.

Why a local check matters before you do anything else

1. Catches typos at the form layer. A client emails you their UTR with one digit transposed. Catch it in your onboarding form, before it propagates into your CRM, accounting package, and HMRC submissions.
2. Works offline.You can validate during data cleanup, batch ETL, or while you're on a flight. No round trip to HMRC. No third-party API to sign up for.
3. Keeps the numbers private. A UTR plus a name is enough to file a fraudulent return. The fewer hops it makes through random web services, the better. This tool never sends anything anywhere.

From bank statement to UTR: a workflow

A common reason people land here: they're reconciling a quarterly client export from their bank, want to confirm the UTRs they have on file match what's in the "HMRC payment reference" column. The clean way to do that:

1. Convert your bank statement PDF to a spreadsheet using our bank statement converter. You get a clean CSV with date, description, amount, and balance for every line.
2. Filter for descriptions starting with HMRC — the ten-digit token in the description is the UTR the payment was allocated to.
3. Copy that column, paste it here, one per line. We flag any that fail the format or advisory checksum, plus any look-alikes (a NINO sneaks into the column surprisingly often).
4. For passes, click Verify on HMRCto open the Self Assessment login page and look up the taxpayer record directly — that's the canonical source.

What this tool does not do

• It does not query HMRC.HMRC does not publish a free public UTR lookup. There's no API a third party can use to confirm a UTR is live and belongs to a given taxpayer without authenticating as that taxpayer. To verify a specific UTR, the taxpayer logs into gov.uk Self Assessment or asks HMRC by post.
• It does not block on the advisory checksum.See above — HMRC don't publish the algorithm, so a failing advisory check is a hint, not a verdict.
• It does not validate NINOs, VAT numbers, or company numbers in depth.When we detect them, we just tell you the shape doesn't match a UTR. VAT has its own modulus-97 check; Companies House numbers have their own format conventions; we leave those to dedicated tools.
• It does not link a UTR to a taxpayer name. That's by design — HMRC treat UTRs as semi-private and there's no public name lookup.

Common reasons a real UTR fails our checker

• Wrong digit count. A UTR is exactly 10 digits. Two digits short? Probably a Companies House number. One digit short? Probably a VAT number without the GB prefix. One digit long? Probably you typed an extra digit.
• You pasted the NINO instead.If the result shows two letters, six digits, one letter — that's a NINO. HMRC use it for PAYE Income Tax coding; it's a tax reference, but it isn't a UTR.
• OCR'd the wrong character. A "0" vs "O", a "1" vs "l", or two transposed digits. The advisory mod-11 check catches the vast majority of single-digit OCR errors.
• Trailing K mis-typed as something else. If you meant 1234567890K and typed 1234567890k, that's fine — we lowercase normally. But 1234567890Xisn't a UTR.
• Spaces vs no spaces. The 5-5 split HMRC uses on printed notices (12345 67890) is just formatting — we strip whitespace. The number itself doesn't include the space.

For developers

Embedding UTR validation in your own application is about 20 lines of any language. The format check is trivial (strip non-digits, assert length 10, assert not all-zero); the advisory mod-11 is the(11 − sum mod 11) mod 11formula above. Pin a test against a known-pass and a known-bad value, document the "HMRC doesn't officially publish" caveat in your tooltip, and you have a reliable client-side check.