# Northern Ireland VAT number format

Source: https://veriport.io/vat-number-format/xi (published 2026-10-28)

A Northern Ireland VAT identification number is the prefix XI followed by 9 or 12 digits, or GD/HA + 3 digits; XI110305878 is a well-formed example. The national check digit is public, so a mistyped number is caught before VIES is asked. Structure as published in the Commission’s VIES FAQ, consulted 2026-10-24.

## Structure

Prefix `XI`, then 9 or 12 digits, or GD/HA + 3 digits. The regular expression the API applies to the part after the prefix is `^(?:[0-9]{9}|[0-9]{12}|(?:GD|HA)[0-9]{3})$`; letters are upper-cased and spaces, dots and dashes removed before the test.

| Country prefix | Structure | Example | Public check digit |
|---|---|---|---|
| XI | 9 or 12 digits, or GD/HA + 3 digits | XI110305878 | yes, verified before VIES |

## The check digit

Northern Ireland publishes the algorithm of its check digit, so an impossible number is refused before VIES is asked: the answer says `structure.checksum: "failed"`, costs nothing and reaches no upstream. The same algorithms are implemented by the open libraries (jsvat, python-stdnum).

## How to validate it

The structure says whether a string can be a Northern Ireland VAT number; only VIES says whether it is registered. The free check below asks VIES live and shows the registered name and address where Northern Ireland publishes them; the API does the same from your code.

```bash
curl "https://veriport.io/api/v1/vat/validate?number=XI110305878"
```

## What a valid answer proves

That the number was registered for intra-EU trade at the moment of the check. Keep the date and, on paid tiers, the VIES consultation number: together they are the evidence a tax audit asks for when an intra-EU supply was zero-rated.

## Questions

### How many digits does a Northern Ireland VAT number have?

9 or 12 digits, or GD/HA + 3 digits, after the two-letter prefix XI: XI110305878 is an example.

### Is XI110305878 a real VAT number?

It is a well-formed example used in the documentation; whether it is registered today is VIES’s answer, not this page’s. Check it with the free tool.

### Why is Northern Ireland in VIES?

Under the Windsor Framework, Northern Ireland follows EU VAT rules for goods; XI numbers are in VIES for goods only. The rest of the UK is not in VIES; its numbers are checked through HMRC (on the roadmap).

## Read next

- [VAT number formats of every member state](https://veriport.io/vat-number-format)
- [Free VAT number check](https://veriport.io/tools/vat-number-check)
- [The VAT validation API](https://veriport.io/vat-validation-api)

## Sources

- VIES — VAT Information Exchange System: FAQ and VAT number structures (Q11) — https://ec.europa.eu/taxation_customs/vies/#/faq (2026-10-24)
- VIES REST API — check-vat-number, check-status (technical information) — https://ec.europa.eu/taxation_customs/vies/#/technical-information (2026-10-24)