When a customer no longer needs an account, request its closure through the API. Closure is an asynchronous process: Modern Treasury validates the request, moves the Internal Account to pending_closure, and returns closed once the account is terminally closed.

Requirements

Before requesting closure, make sure the account meets each of the following:

• Zero balance. The available, pending, and posted balances must all be 0. Sweep or withdraw any remaining funds first, and confirm with Retrieving Account Balances.
• No in-flight transfers. All Payment Orders, Returns, and Reversals on the account must be completed or cancelled.

Request a Closure

Send a PATCH request to the Update Internal Account endpoint with status set to pending_closure. Only pending_closure is accepted for status; any other non-blank value is rejected, and status cannot be combined with another updatable attribute.

curl --request PATCH \
     -u ORGANIZATION_ID:API_KEY \
     --url https://app.moderntreasury.com/api/internal_accounts/<internal_account_id> \
     -H 'content-type: application/json' \
     -d '{
       "status": "pending_closure"
     }'

A successful request returns the full Internal Account with a status of pending_closure. The example below is abridged; see the Internal Account object for every field.

{
  "id": "bf5f1df9-de01-40c2-9040-7ec10170a14c",
  "object": "internal_account",
  "name": "Customer Payment Account",
  "status": "pending_closure",
  "currency": "USD",
  "legal_entity_id": "8f4e2b1c-7d93-4a56-b8e1-2c9f0a3d5e67",
  "parent_account_id": null,
  "counterparty_id": null,
  "live_mode": true,
  "metadata": {},
  "created_at": "2026-01-01T16:30:00Z",
  "updated_at": "2026-02-14T09:15:00Z"
}

Closure States

An account stays in pending_closure until the closure finishes processing, which can take several business days.

Subscribe to internal_account webhooks to be notified when the closure completes. You will receive an internal_account.closed webhook once the account reaches closed.

Failure Responses

Rejected closures return a 422 with the reason in errors.message and leave the account in its previous status, either active or suspended; a failed request never leaves the account in pending_closure. Errors prefixed with vendor_rejected are surfaced from downstream checks run against the most up-to-date account state.

A non-zero balance:

{
  "errors": {
    "code": "parameter_invalid",
    "message": "vendor_rejected: Account must have a zero balance to be closed",
    "parameter": "base"
  },
  "error_list": [
    {
      "code": "parameter_invalid",
      "message": "vendor_rejected: Account must have a zero balance to be closed",
      "parameter": "base"
    }
  ]
}

In-flight transfers on the account:

{
  "errors": {
    "code": "parameter_invalid",
    "message": "The internal account has in-flight PaymentOrders.",
    "parameter": "internal_account"
  },
  "error_list": [
    {
      "code": "parameter_invalid",
      "message": "The internal account has in-flight PaymentOrders.",
      "parameter": "internal_account"
    }
  ]
}

An account in a state that cannot be closed, such as one that is already closed or still pending activation:

{
  "errors": {
    "code": "parameter_invalid",
    "message": "vendor_rejected: Account is not in a state that can be closed",
    "parameter": "base"
  },
  "error_list": [
    {
      "code": "parameter_invalid",
      "message": "vendor_rejected: Account is not in a state that can be closed",
      "parameter": "base"
    }
  ]
}