Developer API
Verify UK companies, VAT numbers and postcodes programmatically for checkout tax decisions, supplier onboarding, KYC and lead enrichment. Single lookups are free; paid plans add quota, bulk CSV and priority rate limits.
Try it now, free
No API key needed for individual lookups — try live examples right now:
Endpoints
/api/v1/company?crn={crn}Full Companies House profile for a company number.
/api/v1/company?q={name}Search companies by name, returns top matches.
/api/v1/vat?vat={vatNumber}Validate a UK VAT number against HMRC in real time.
/api/v1/postcode?postcode={postcode}Full postcode geography, council and ULEZ info.
/api/v1/bulkBatch lookups (companies / VAT / postcodes) in one call — CSV-ready.
Batch check (bulk CSV)
curl -X POST "https://qxx.uk/api/v1/bulk" \
-H "Content-Type: application/json" \
-H "x-api-key: YOUR_API_KEY" \
-d '{"type":"company","items":["00445790","00488639"]}'Free tier: 5 rows per batch. Accountant Pro: 5,000 rows + CSV export from the dashboard.
Authentication & quotas
Paid subscribers receive an API key after checkout. Send it in the x-api-key header. Quotas reset monthly on your signup date.
curl -H "x-api-key: YOUR_API_KEY" \ "https://qxx.uk/api/v1/company?crn=00445790"
Status codes: 401 invalid key · 402 subscription inactive · 429 quota exceeded / rate limited · 404 record not found.
Plans built for each job
API Starter
$9.99/mo
- 10,000 API calls / month
- Priority rate budget
- VAT + company + postcode
Accountant Pro
$29/mo
- 5,000-row CSV batches
- Filing-deadline alerts
- 50,000 API calls / month
Credit Pack
$3 / report
- No-watermark PDF reports
- Timestamps + source watermark
- Archive-ready for risk files
Lead Export
$29 / 5,000 rows
- SIC / address / incorporation year
- Active-company filter
- CSV download for cold email
All data is sourced from official UK public registers under the Open Government Licence v3.0. Checkout is handled by Lemon Squeezy (preferred) or Stripe — see /pricing to subscribe.