# Agent402 UK VAT Number Format Validator

> Agent402 UK VAT Number Format Validator is a paid API for AI agents from agent402.co.uk, paid per call via x402, $0.001/call, status down (last checked 2026-09-15).

Validates UK VAT number format (GB/XI prefix + digits, or GD/HA) using pure logic — no live HMRC or VIES lookup required.

## Facts

- Endpoint: POST https://agent402.co.uk/v1/validate/uk-vat
- Price: $0.001/call
- Payment: x402
- Status: down
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/agent402-uk-vat-number-format-validator-8fb36af8
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_wCuTrBXQdbN_jc5zxjJb7

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 agent402-uk-vat-number-format-validator-8fb36af8 -d '<json body>'
```

Example prompt: Before we proceed with this invoice, can you check whether 'GB123456789' is a correctly formatted UK VAT number?

## When to prefer this

Use this endpoint when you need a fast, cheap, offline-style format check on a UK VAT number before invoking live HMRC or VIES verification. Ideal as a pre-action gate in tax workflows, invoice processing pipelines, or business onboarding flows where you want to catch obviously malformed VAT numbers without incurring network latency or rate limits from government APIs.

## Known failure modes

- Invalid or missing 'vat' field returns valid_format: false
- Unrecognized prefix (not GB, XI, GD, HA) returns valid_format: false
- Wrong digit count for GB/XI (must be 9 or 12 digits) returns valid_format: false
- Empty string input may return an error or valid_format: false
- Non-string input may cause a 400 or schema error

## How this service works

Don't burn tokens on deterministic work. Go/no-go jobs first: payout preflight, text firewall (PII/secrets), budget check — then rails, calendars, finmath. x402 USDC on Base. UK + global. agent402.co.uk — not agent402.tools. $0.001–$0.002 USDC on Base. No API keys.

## Output

Returns a JSON object with the parsed VAT prefix (e.g. 'GB', 'XI', 'GD', 'HA'), the normalized electronic format string, and a boolean 'valid_format' field indicating whether the number conforms to UK VAT formatting rules. Does not confirm HMRC registration status.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "vat": {
   "type": "string",
   "description": "VAT number"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "prefix": "GB",
  "electronic": "GB123456789",
  "valid_format": true
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/agent402-uk-vat-number-format-validator-8fb36af8/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from agent402.co.uk](https://www.zero.xyz/host/agent402.co.uk/llms.txt)