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Validate Singapore Tax ID Numbers via API
When building B2B applications that serve Singapore (Singapore / 新加坡), validating your customers' GST 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 Singapore GST Registration Number numbers via IRAS (Inland Revenue Authority of Singapore). Every request returns the validation status with sub-100ms response times for cached results.Singapore applies a standard rate of 9% (GST Registration Number).
QUICK START
curl -H "Authorization: Bearer YOUR_API_KEY" \ http://localhost:3000/api/v1/validate/SG/199900888E
Code examples
Choose your language. Every example validates a Singapore VAT number and returns the registration status with company details.
const res = await fetch('http://localhost:3000/api/v1/validate/SG/199900888E', {
headers: { 'Authorization': 'Bearer YOUR_API_KEY' }
});
const data = await res.json();
// { valid: true, status: "active", company_name: "...", country_code: "SG", cached: false }
console.log(data);When to validate Singapore tax ID numbers
B2B invoicing and accounts payable
When issuing or receiving invoices from Singapore businesses, validating the GST 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 Singapore business customers, collecting and validating their GST 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 Singapore sellers or vendors, validating the GST 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 Singapore VAT format (GST Registration Number)
Singapore raised its GST rate from 8% to 9% in January 2024. Businesses with taxable turnover exceeding SGD 1 million must register for GST. The GST registration number is typically the company's UEN (Unique Entity Number) followed by a check letter.
| Field | Value |
|---|---|
| Country code | SG |
| Local name | GST Registration Number |
| Format | 9 digits + 1 letter |
| Regex pattern | ^[0-9]{9}[A-Z]$ |
| Example | 199900888E |
| VIES supported | No |
VAT rates in Singapore
Singapore applies a standard GST Registration Number rate of 9%.
| Rate type | Percentage | Currency |
|---|---|---|
| Standard rate | 9% | SGD |
Frequently asked questions
What is the Singapore tax ID number format?
Singapore tax ID numbers (GST Registration Number) follow the format: 9 digits + 1 letter. A valid example is 199900888E. The TaxID API validates the format locally and where possible checks against the IRAS (Inland Revenue Authority of Singapore), ensuring you only accept properly registered businesses.
Should I validate GST Registration Number numbers when transacting with Singapore businesses?
Validating GST 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 Singapore?
The standard tax rate in Singapore is 9% (GST Registration Number). Singapore applies a single flat rate with no reduced rates. The TaxID API's /rates endpoint returns all current rates for programmatic access.
How long does Singapore 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 IRAS (Inland Revenue Authority of Singapore), 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 Singapore GST Registration Number numbers?
The TaxID API validates Singapore GST Registration Number numbers in two steps: first it checks the format against the official pattern (9 digits + 1 letter), then it queries IRAS (Inland Revenue Authority of Singapore) where a live API is available. Singapore raised its GST rate from 8% to 9% in January 2024. Businesses with taxable turnover exceeding SGD 1 million must register for GST. The GST registration number is typically the company's UEN (Unique Entity Number) followed by a check letter.
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