Usage and credits
What is metered, what costs credits, and what a 402 means.
Every authenticated call is metered per day and operation; GET /v1/usage returns the window you ask for (from, to; at most 92 days; the last 30 by default) with totals per operation and per day. Calculations are usage: metered, never charged in credits.
Credits pay for billable filing actions on live keys and are consumed once per request (the request id is the idempotency key, so a retry never double-charges). GET /v1/credits returns the balance and recent movements. A live operation that needs more credits than the workspace holds answers 402 CREDITS_REQUIRED with required, balance and credits_url. Sandbox never bills. Credits are added from the developer console; purchase rails are being connected.
{ "error": "This operation needs 1 credit; the workspace holds 0.", "code": "CREDITS_REQUIRED", "requestId": "…", "required": 1, "balance": 0, "credits_url": "https://app.taxpio.com/app/developers/usage" }