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Validate United Kingdom Tax ID Numbers via API
When building B2B applications that serve United Kingdom (United Kingdom), validating your customers' VAT Registration Number is essential for B2B compliance and protecting your business from tax liability.
The TaxID API provides instant format validation and live lookup for United Kingdom VAT Registration Number numbers via HMRC (His Majesty's Revenue and Customs). Every request returns the validation status with sub-100ms response times for cached results.United Kingdom applies a standard rate of 20% (VAT Registration Number).
QUICK START
curl -H "Authorization: Bearer YOUR_API_KEY" \ http://localhost:3000/api/v1/validate/GB/GB123456789
Code examples
Choose your language. Every example validates a United Kingdom VAT number and returns the registration status with company details.
const res = await fetch('http://localhost:3000/api/v1/validate/GB/GB123456789', {
headers: { 'Authorization': 'Bearer YOUR_API_KEY' }
});
const data = await res.json();
// { valid: true, status: "active", company_name: "...", country_code: "GB", cached: false }
console.log(data);When to validate United Kingdom tax ID numbers
B2B invoicing and accounts payable
When issuing or receiving invoices from United Kingdom businesses, validating the VAT Registration Number ensures the identifier is genuine before committing the transaction to your ERP. Invalid or fabricated tax IDs are a leading vector for invoice fraud and can result in rejected filings or audit penalties.
SaaS and e-commerce checkout
If your platform serves United Kingdom business customers, collecting and validating their VAT Registration Number at checkout is required for accurate tax treatment, correct invoicing, and downstream reporting. An invalid tax ID at the point of sale creates a correction burden across your finance stack.
Supplier and marketplace onboarding
For procurement platforms and regulated marketplaces onboarding United Kingdom sellers or vendors, validating the VAT Registration Number at registration prevents fraudulent or duplicate accounts from entering your ecosystem. Validate once at onboarding, then re-validate periodically to detect deregistrations or changes.
About United Kingdom VAT format (VAT Registration Number)
Since Brexit (January 2021), the UK is no longer part of the EU VAT system and cannot be validated via VIES. UK VAT numbers are validated directly through the HMRC API. UK businesses selling digitally to EU customers must register for VAT in an EU member state or use the OSS scheme.
| Field | Value |
|---|---|
| Country code | GB |
| Local name | VAT Registration Number |
| Format | GB + 9 digits |
| Regex pattern | ^GB[0-9]{9}$ |
| Example | GB123456789 |
| VIES supported | No |
VAT rates in United Kingdom
United Kingdom applies a standard VAT Registration Number rate of 20%. Reduced rates of 5% apply to essential goods and services.
| Rate type | Percentage | Currency |
|---|---|---|
| Standard rate | 20% | GBP |
| Reduced rate | 5% | GBP |
Frequently asked questions
What is the United Kingdom tax ID number format?
United Kingdom tax ID numbers (VAT Registration Number) follow the format: GB + 9 digits. A valid example is GB123456789. The TaxID API validates the format locally and where possible checks against the HMRC (His Majesty's Revenue and Customs), ensuring you only accept properly registered businesses.
Should I validate VAT Registration Number numbers when transacting with United Kingdom businesses?
Validating VAT Registration Number numbers reduces fraud risk, prevents invalid identifiers from entering your accounting system, and is required by many B2B contracts and procurement platforms. While mandatory rules vary by jurisdiction, validating at onboarding is widely considered best practice — especially for SaaS, marketplace, and fintech platforms with global customer bases.
What is the standard tax rate in United Kingdom?
The standard tax rate in United Kingdom is 20% (VAT Registration Number). Reduced rates of 5% apply to certain goods and services such as food, books, and medical supplies. The TaxID API's /rates endpoint returns all current rates for programmatic access.
How long does United Kingdom tax ID validation take with TaxID?
For cached results (previously validated in the last 24 hours), the TaxID API responds in under 10ms. Format validation is instantaneous. For uncached requests requiring a live lookup against HMRC (His Majesty's Revenue and Customs), response time is typically 100–500ms. Valid numbers are cached for 24 hours; invalid numbers are cached for 1 hour.
How does the TaxID API validate United Kingdom VAT Registration Number numbers?
The TaxID API validates United Kingdom VAT Registration Number numbers in two steps: first it checks the format against the official pattern (GB + 9 digits), then it queries HMRC (His Majesty's Revenue and Customs) where a live API is available. Since Brexit (January 2021), the UK is no longer part of the EU VAT system and cannot be validated via VIES. UK VAT numbers are validated directly through the HMRC API. UK businesses selling digitally to EU customers must register for VAT in an EU member state or use the OSS scheme.
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