Update a Bank Counterparty

Changes a US withdrawal destination. A field left out keeps its stored value, and sending "" does not clear one. reference, customer_id and coin cannot change. A body with no fields returns the counterparty unchanged.

The payment is checked only when the patch sends a payment field (instrument, wire_type, account_type, routing_number, account_number, swift or iban). The check is of the stored payment with those fields laid over it, under the same rules as a save. Changing the rail means sending every field the new rail needs that the stored one does not already have: an ACH turned into an international wire needs wire_type, swift, and an IBAN when it has no account number. A patch that only changes the name, the holder, the bank name or an address does not re-check the account, so a destination v2 saved with a routing number this API would refuse can still be renamed.

Changing the routing number, account number, SWIFT or IBAN of a destination the bank already knows drops that link, so the next withdrawal opens one for the new account. A destination whose status is needs_update becomes active, and status_reason is left out of the response, when the account it pays changes — including one the bank had not registered yet.

Sending address replaces the holder's address, and the object has to be complete. Sending any field of bank_address replaces the bank's address the same way. There is no idempotency header and no webhook.

An account-scoped key updates only its own account's counterparties; another account's reads as 404. A workspace-scoped key updates any US counterparty of the workspace.

Replaces PUT /api/v2/banking/counterparties/{id}.

Authorization:

Every request is signed with your API key: a short-lived JWT, signed with your private key, sent in one header on /v3/* and /api/v2/* alike.

Headers:
  Authorization: APIKey {SIGNED_JWT}

How to build and sign the JWT: Authentication.

Endpoint

PATCH

/v3/banking/counterparties/{counterparty_id}

Path parameters

Parameter	Type	Description
counterparty_id	string (bcp_…)	Required. The counterparty.

Request Body Sample

{
  "name": "Northwind Holdings LLC"
}

Request Body Schema

Every field is optional. The types and bounds are the ones on Save a Bank Counterparty.

Field	Description
name	The new name, 2 to 255 characters.
holder_type	individual or business.
bank_name	The bank, 2 to 255 characters.
instrument, wire_type, account_type, routing_number, account_number, swift, iban	Laid over the stored payment, then checked. See above.
address	Replaces the holder's address. Send the whole address.
bank_address	Replaces the bank's address. Send the whole address.

Response Sample

{
  "id": "bcp_01k8z5q7r9s1t3v5w7x9y1z3a5",
  "customer_id": "cst_01h455vb4pex5vsknk084sn02q",
  "reference": "vendor-42",
  "coin": "USD",
  "name": "Northwind Holdings LLC",
  "holder_type": "business",
  "bank_name": "Chase",
  "instrument": "ach",
  "account_type": "checking",
  "routing_number": "021000021",
  "account_number": "000123456789",
  "status": "active",
  "address": {
    "line1": "1 Market Street",
    "line2": "Suite 400",
    "city": "San Francisco",
    "state": "CA",
    "postal_code": "94105",
    "country": "US"
  },
  "created_at": "2026-10-23T12:00:00Z",
  "updated_at": "2026-10-23T18:12:00Z"
}

Response Schema

The counterparty, with the fields of a List Bank Counterparties row, without customer.

Errors

Status	message	When
400	failed to parse request	The body is not valid JSON, counterparty_id is not a bcp_… id, or a sent enum is not one of its values.
400	invalid_holder_name	name is shorter than 2 characters once spaces are collapsed.
400	invalid_holder_type	holder_type is not individual or business.
400	invalid_bank_name	bank_name is shorter than 2 characters.
400	invalid_address	An address that was sent is incomplete or out of bounds.
400	invalid_instrument	instrument is not ach or wire.
400	invalid_wire_type	The payment, after the patch, is a wire without domestic or international.
400	invalid_account_type	The payment, after the patch, is an ACH without checking or savings.
400	invalid_routing_number	The payment, after the patch, fails the routing rule of its rail.
400	invalid_account_number	The payment, after the patch, fails the account-number rule of its rail.
400	invalid_swift	An international wire whose SWIFT is not 8 or 11 letters and digits.
400	invalid_iban	An IBAN that is not 15 to 34 letters and digits.
401	unauthorized	Missing or invalid signature.
404	bank_counterparty_not_found	No such counterparty, it belongs to another account, it was deleted, or the id is not a US counterparty.
422	Validation failed	A sent text field or number is longer than allowed; details names it.

Coming from v2

v2 (PUT /api/v2/banking/counterparties/{id})	v3
PUT	PATCH; a field left out keeps its stored value
id (uuid)	counterparty_id (bcp_…)
the same camelCase body as create	the same snake_case body as create, every field optional

Support and Resources

If you need assistance or have any questions, our support team is here to help. You can contact our support team at support@blockwyre.com.

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