Spending you record yourself, posted the moment you send it.

• Leave entityId out only when this key can reach exactly one business. When it can reach several, a call that omits it is refused; call GET /businesses for the ids.
• Send exactly one of vendorName or vendorId.
• A vendorName that matches no existing vendor exactly creates a new one, so prefer vendorId when you have it. The match is case sensitive.
• amountCents must be greater than zero.
• The account you send is posted as it is. Nothing here is categorized by AI, and nothing lands in the review queue.

Needs the expenses:write permission. Only a Read and write key has it.

curl -X POST "https://www.numm.io/api/v1/expenses" \
  -H "Authorization: Bearer nmo_live_REPLACE_WITH_YOUR_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: 0190a1b2-c3d4-7e5f-8a9b-0c1d2e3fee00" \
  -d '{
  "entityId": "0190a1b2-c3d4-7e5f-8a9b-0c1d2e3f1002",
  "date": "2026-02-01",
  "amountCents": "1500",
  "vendorId": "0190a1b2-c3d4-7e5f-8a9b-0c1d2e3f1004",
  "accountId": "0190a1b2-c3d4-7e5f-8a9b-0c1d2e3f1003"
}'

{
  "expenseId": "0190a1b2-c3d4-7e5f-9a9b-0c1d2e3f100a",
  "transactionId": "0190a1b2-c3d4-7e5f-9a9b-0c1d2e3f1006"
}

This call takes an optional Idempotency-Key header. Repeat the same request with the same key within 24 hours and you get the first response back, with an idempotent-replayed: true header, and the work does not run twice. The same key with a different request is refused. See Idempotency and safe retries.