# Verify UK VAT Number Format & Check-Digit Validator

> Verify UK VAT Number Format & Check-Digit Validator is a paid API for AI agents from verify-uk.verifyuk.workers.dev, paid per call via x402, $0.001/call, status unknown (last checked 2026-10-30).

Validates a UK VAT number's format and HMRC check-digit (mod 97/9755) without making a live HMRC registration call

## Facts

- Endpoint: GET https://verify-uk.verifyuk.workers.dev/v1/validate/vat?utm_source=zero.xyz
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-30
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/verify-uk-vat-number-format-check-digit-validator-09ca36f5
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_Lc9bvPjyii7CdtSCDO5az

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability verify-uk-vat-number-format-check-digit-validator-09ca36f5
```

Example prompt: Can you check whether the VAT number GB123456789 is correctly formatted and passes the HMRC check-digit test — without doing a live HMRC lookup?

## When to prefer this

Use this endpoint when you need fast, free-of-HMRC-quota format and check-digit validation of a UK VAT number — ideal for pre-screening user inputs, catching typos, or filtering obviously fake numbers before spending an HMRC live-lookup call. Prefer this over /v1/business/check when you don't need to confirm active registration, just structural validity.

## Known failure modes

- Missing 'vat' query parameter — returns error indicating required field is absent
- VAT number with invalid characters — flagged as invalid format with explanatory note
- Network timeout on the Cloudflare Worker — transient failure, retry recommended
- VAT number that looks correct in length but fails mod 97/9755 check — returns valid:false with a note explaining the check-digit failure

## How this service works

UK VAT number format + check-digit test: Checks a UK VAT number's format and HMRC check digits (mod 97 / 9755). Catches fake or mistyped VAT numbers instantly without an HMRC call. Use /v1/business/check to confirm live registration.

## Output

A JSON object containing a 'valid' boolean indicating whether the VAT number passes format and check-digit validation, plus a 'notes' array with human-readable explanations of any failures (e.g. wrong length, failed HMRC check-digit test).

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "vat"
     ],
     "properties": {
      "vat": {
       "type": "string",
       "description": "UK VAT number, with or without GB"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "notes": [
   "Right length, but fails the HMRC check-digit test."
  ],
  "valid": false
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/verify-uk-vat-number-format-check-digit-validator-09ca36f5/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from verify-uk.verifyuk.workers.dev](https://www.zero.xyz/host/verify-uk.verifyuk.workers.dev/llms.txt)