Void an issued GST tax invoice
Voids an issued invoice and answers it with cancelled_at set. THIS NEEDS write_india_gst:delete IN ADDITION TO write_india_gst. There is no un-cancel: the void frees the order’s slot, so putting the order right means issuing a SECOND invoice that consumes another number, and the buyer’s copy of the original stops matching the merchant’s books. Nothing errors and every read still answers 200; the loss surfaces in the return the merchant files. A POST RATHER THAN A DELETE because nothing is removed. The row keeps its number and stays readable and listed forever, which is what makes the void auditable. AN ALREADY-CANCELLED INVOICE IS 409, not 404 and not a second success. Retrying a cancel that already landed must not read as “this invoice never existed”, because the two call for opposite next steps. The cancel is still idempotent BY KEY: replaying an Idempotency-Key returns the stored 200. It is a NEW key against a voided invoice that answers 409.
Authorizations
A secret API key. Publishable keys cannot reach this API. A key may carry an expiry, and an expired key is refused exactly like an unknown one, with a 401 that names no reason; check the key's expires_at in the dashboard rather than inferring it from a response. When a merchant rolls a key's secret they choose a grace window of up to 3 days, and for its duration BOTH the new secret and the one it replaced authenticate, so an integration moves over on its own deploy schedule instead of at the instant the button is pressed. Move before the window closes: after it, the old secret is refused. Nothing else about this contract moves with a roll. The key keeps its id and its scopes, so the only thing an integration updates is the credential itself.
Headers
A unique key per logical write. Replaying a request with the same key returns the first response byte for byte instead of applying the write twice.
Path Parameters
Body
Takes no parameters, and an empty body is expected. The response is the invoice with cancelled_at set. THIS NEEDS write_india_gst:delete AS WELL AS write_india_gst. There is no un-cancel. The void frees the order's slot, so putting the order right means issuing a SECOND invoice that consumes another number, and the buyer's copy of the original stops matching the merchant's books. Nothing errors and every read still answers 200; the loss surfaces in the return the merchant files. A POST RATHER THAN A DELETE because nothing is removed: the row keeps its number and stays readable and listed forever, which is what makes the void auditable. AN ALREADY-CANCELLED INVOICE IS 409, not 404 and not a second success. Retrying a cancel that already landed must not read as "this invoice never existed", because the two call for opposite next steps. USE A FRESH Idempotency-Key. A replayed key returns the stored 200 without re-running anything.
Response
Success