POST

Register an account number

ENDPOINT/v1/financial-accounts/{financial_account_id}/account-numbers

Attaches an account number to this financial account. ACH_RECEIVING and WIRE_RECEIVING numbers take a routing number and account number and let the financial account receive inbound credits. LEDGER numbers are allocated by Rook to track a class of transactions in the books. A financial account may hold several numbers, one per purpose. The response masks account_number and returns account_number_last4. Send Idempotency-Key so retries return the original registration.

Authentication & Headers

Header	Type	Requirement	Description
Authorization	string	REQUIRED	API key passed as an HTTP Bearer token: `Bearer rk_live_...`
X-Program-ID	UUID	PROGRAM-SCOPED	Program boundary UUID that scopes the issuing card, wallet, or transfer.
Content-Type	string	REQUIRED	Must be `application/json`.
Idempotency-Key	string	OPTIONAL	Unique UUID to prevent duplicate execution of financial creations or mutations.

Path Parameters

Parameter	Type	Requirement	Description
financial_account_id	string	REQUIRED	Unique identifier of the financial account.

Request Body Schema

application/json

purposestring

REQUIRED

What the account number is used for. `ACH_RECEIVING` and `WIRE_RECEIVING` are rail-facing numbers with a `routing_number`, used to receive inbound credits. `LEDGER` is an internal ledgering number used to track a class of transactions in the financial account's books; it has no routing number.

Enum values:ACH_RECEIVINGWIRE_RECEIVINGLEDGER

routing_numberstring

optional

Nine-digit ABA routing number for inbound ACH and wire.

account_numberstring

optional

Full account number. Write-only; never echoed on the response. Digits only.

Response Codes & Schemas

201The registered account number, with account_number masked.

application/json

{
  "id": "6e1b4c80-9d25-4f37-a8c2-1b7e5d0f3948",
  "object": "account_number",
  "financial_account_id": "9b3e1c70-4d2a-4f86-8c1b-5e7a2d9f0c14",
  "purpose": "ACH_RECEIVING",
  "routing_number": "021000021",
  "account_number": "••••••••6789",
  "account_number_last4": "6789",
  "created_at": "2026-08-12T10:20:00Z",
  "updated_at": "2026-08-12T10:20:00Z"
}

400Bad Request: malformed JSON, failed schema validation, or conflicting parameters.

application/json

{
  "error": {
    "type": "invalid_request_error",
    "code": "invalid_request",
    "message": "invalid order by: foo. Valid options are: [created_at updated_at]",
    "param": "order_by",
    "request_id": "550e8400-e29b-41d4-a716-446655440000",
    "doc_url": "https://docs.rookpayments.com/errors/invalid_request"
  }
}

401Unauthorized: missing, malformed, or unknown API key.

application/json

{
  "error": {
    "type": "authentication_error",
    "code": "authentication_error",
    "message": "A valid API key is required.",
    "param": null,
    "request_id": "550e8400-e29b-41d4-a716-446655440000",
    "doc_url": "https://docs.rookpayments.com/errors/authentication_error"
  }
}

403Forbidden: the API key is denied by RBAC, or it cannot access this program. A resource that exists on another program or organization returns `404 not_found`, not `403`.

application/json

{
  "error": {
    "type": "permission_error",
    "code": "permission_denied",
    "message": "The API key cannot access this program.",
    "param": "X-Program-ID",
    "request_id": "550e8400-e29b-41d4-a716-446655440000",
    "doc_url": "https://docs.rookpayments.com/errors/permission_denied"
  }
}

404Not Found: unknown id, or the resource is not visible to this API key.

application/json

{
  "error": {
    "type": "not_found_error",
    "code": "not_found",
    "message": "No card found for the given id.",
    "param": "card_id",
    "request_id": "550e8400-e29b-41d4-a716-446655440000",
    "doc_url": "https://docs.rookpayments.com/errors/not_found"
  }
}

409Conflict: incompatible state, or Idempotency-Key reused with a different body.

application/json

{
  "error": {
    "type": "conflict_error",
    "code": "conflict",
    "message": "The card cannot be reissued from its current state.",
    "param": null,
    "request_id": "550e8400-e29b-41d4-a716-446655440000",
    "doc_url": "https://docs.rookpayments.com/errors/conflict"
  }
}

422Unprocessable Entity: the document is valid JSON but violates a business rule.

application/json

{
  "error": {
    "type": "invalid_request_error",
    "code": "insufficient_funds",
    "message": "The source financial account does not have enough available balance.",
    "param": "amount",
    "request_id": "550e8400-e29b-41d4-a716-446655440000",
    "doc_url": "https://docs.rookpayments.com/errors/insufficient_funds"
  }
}

429Too Many Requests: the API key exceeded its rate limit.

application/json

{
  "error": {
    "type": "rate_limit_error",
    "code": "rate_limited",
    "message": "Rate limit exceeded. Retry after the number of seconds in Retry-After.",
    "param": null,
    "request_id": "550e8400-e29b-41d4-a716-446655440000",
    "doc_url": "https://docs.rookpayments.com/errors/rate_limited"
  }
}

500Internal Server Error: unexpected failure. Retry with the same Idempotency-Key.

application/json

{
  "error": {
    "type": "api_error",
    "code": "internal_error",
    "message": "An unexpected error occurred. Retry with the same Idempotency-Key.",
    "param": null,
    "request_id": "550e8400-e29b-41d4-a716-446655440000",
    "doc_url": "https://docs.rookpayments.com/errors/internal_error"
  }
}