# Simulate incremental authorization

**POST** `/simulate/issuing/card-transactions/{card_transaction_id}/incremental-authorization`

Simulate an incremental authorization that adds to an existing authorization hold, such as a hotel stay extension.
Currency codes are preserved from the initial authorization.

The original transaction must have started as an authorization, not a full financial transaction, and must not have
captured funds. Column sends a real-time authorization decision request for the increment to your endpoint subscribed
to `decision.issuing.card_transaction`, and declines if none is configured.

### Path Parameters

- `card_transaction_id` `string` _(required)_ — Unique identifier for the card transaction.

### Body Parameters

- `cardholder_amount` `number` _(required)_ — Additional cardholder amount to authorize, expressed in the smallest currency unit
  (e.g., cents for `USD`). This amount will be added to the existing authorization hold.
  Must not exceed 999999999999.
- `fx_rate` `string` — Foreign exchange rate for multi-currency transactions, as a decimal string.
  If not provided, uses the original transaction's FX rate.

**Request**

```shell
curl 'https://api.column.com/simulate/issuing/card-transactions/<card_transaction_id>/incremental-authorization' \
  -XPOST \
  -u :<YOUR API KEY> \
  -H 'Content-Type: application/json' \
  -d '{
  "cardholder_amount": 5000,
  "fx_rate": "1.10"
}'
```

**Response 200**

```json
{
  "card_account_id": "cacc_2x8gszy5folpA9s0TOCseE9ABDM",
  "card_id": "card_2x8gszy5folpA9s0TOCseE9ABDM",
  "card_program_id": "cpgm_2x8gszy5folpA9s0TOCseE9ABDM",
  "created_at": "2024-01-15T09:30:00Z",
  "id": "ctxn_2x8gszy5folpA9s0TOCseE9ABDM"
}
```