Quaderno vs TaxCloud

Quaderno

A public OpenAPI 3.1 spec covers 92 operations, with a free sandbox and a status page showing no incident since July 2025. The API key has full account access, there are no idempotency keys, and the newest public API version is dated October 2024.

TaxCloud

A 30-operation REST API with a public OpenAPI 3.1 contract, llms.txt, Markdown docs and a 30-day trial that needs no card. The vendor publishes no rate limit numbers, no SLA, no API changelog and no official v3 client library, and the security page names no audit or certification.

Quaderno

1. Call GET https://quadernoapp.com/api/authorization first. Its href gives the account subdomain that every other call needs
2. Before retrying a failed POST /transactions, list invoices by processor_id to check whether the sale was recorded. There is no idempotency key
3. Treat GET /invoices/{id}/deliver as a write. It emails the invoice to the customer
4. Correct a final invoice with a credit note. DELETE on invoices returns 410 and PUT accepts only notes, tags, metadata and address fields
5. Read X-RateLimit-Remaining and X-RateLimit-Reset, and page with created_before and limit up to 100

TaxCloud

1. Send X-API-KEY on every call and put the connection ID in the path, as in /tax/connections/{connectionId}/carts. A wrong ID returns 404
2. Mark nexus states active in the account first. With none active the API returns zero tax and no error
3. Use a separate test connection. There is no sandbox, and orders on a live connection go into filing
4. Pass a stable idempotencyKey on refunds, and never convert the same cart twice. A second conversion creates a duplicate liability
5. Void a wrong order before 12:00 AM Eastern on the 10th of the month after its completedDate. Later requests return 422