§ PRACTICE · 5 MIN READ
Integrating Countersure into your software
API authentication, request format, webhooks.
Published 2026-04-16 · Countersure
Authentication
API keys are issued from the dashboard. Authenticate with Authorization: Bearer cs_live_xxx.
Test keys (cs_test_xxx) hit a sandbox that returns deterministic responses.
Single check
POST /v1/vat/check with body { vat_number: "GB123456789", requester_vat?: "GB987654321" }.
Returns the same payload format as the website — verification ID, status, registered name and address.