Guide
Calculations and outcomes
Calculate sales tax from seller, customer, item, currency, and transaction details. Review the outcome and returned tax amounts.
Send the facts for this sale
A calculation uses the seller’s effective registrations, the customer location and type, the item tax code, currency, tax behavior, and billing event. Send the commercial date so a retry gives the same dated result.
HTTP 201 means the calculation was saved. Read
outcome before using tax or total.Handle the outcome
calculatedThe API has enough facts to return a final result.
review_requiredMore facts or a review are needed. Do not use these amounts as final.
unsupportedThe API does not support this combination. Do not use these amounts as final.
A saved calculation has its own outcome. You do not need to call the coverage endpoint first.
Request
Shell
curl --request POST \
--url "https://api.salestaxcalculatorapi.com/v1/calculations" \
--header "Authorization: Bearer $SALESTAX_API_KEY"
--header "Content-Type: application/json" \
--header "Idempotency-Key: order-1001-calc" \
--data '{"reference":"order-1001","transaction_date":"2026-08-29","currency":"CAD","tax_behavior":"exclusive","billing_event":"subscription_start","seller":{"country":"CA","channel_role":"direct_legal_supplier","registrations":[{"country":"CA","state":"ON","type":"gst_hst","effective_from":"2026-01-01"}]},"customer":{"type":"consumer","address":{"country":"CA","state":"ON","postal_code":"M5V 2T6"}},"lines":[{"reference":"subscription","amount":"100.00","quantity":"1","tax_code":"saas"}]}'