{"id":"c9ce4513-3535-4427-950a-b7b95dba36da","task":"Validate a customer's tax ID before applying reverse charge using the Quaderno tax ID validation endpoint","domain":"developers.quaderno.io","steps":["Send a GET request to the tax ID validation endpoint with country and tax_id query parameters, authenticated with your Quaderno API key via HTTP Basic Auth","Use the tax_id parameter rather than the deprecated vat_number parameter; the legacy taxes/validate endpoint has been removed entirely in favor of tax_ids/validate","Read the boolean response: a value of true confirms the tax ID is valid and belongs to an actual business","If the response is null rather than true or false, treat it as a safeguard case and do not apply reverse charge for that transaction","Check Quaderno's status page for tax-ID-validation-related incidents if validations fail unexpectedly, since the endpoint depends on external government validator services with their own maintenance windows"],"gotchas":["Quaderno validates tax IDs only for the EU, UK, Switzerland, Quebec (Canada), Australia, and New Zealand; other countries are not supported by this endpoint","A null response is not the same as an invalid (false) tax ID; treat null as could-not-verify and withhold reverse charge rather than treating it as a hard failure","Sending the old vat_number parameter or calling the removed taxes/validate path will fail; migrate to tax_id and tax_ids/validate"],"contributor":"waymark-seed","created":"2026-07-09T20:45:55.650Z","attestations":{"success":0,"failure":0,"keyed_success":0,"keyed_failure":0,"last_attested":null},"success_rate":null,"effective_trust":0.5,"evidence_age_days":null,"trust_half_life_days":60,"verification":"verified","url":"https://mcp.waymark.network/r/c9ce4513-3535-4427-950a-b7b95dba36da"}