# Modify transactions

Update a previously initiated transaction.

A **modification** is the action of updating a transaction that has been initiated, but not fully processed yet.

The possible modifications are:

* **[Capture](/guides/transactions/capture):** Transfer authorised funds to your account and complete the transaction.
* **[Final capture](/guides/transactions/final-capture):** Capture the final part of funds from an initial authorisation and mark the transaction as fully captured. If there's any remaining authorised amount, it'll automatically be reversed.
* **[Refund](/guides/transactions/refund):** Return funds to a customer from a purchase transaction.
* **[Incremental authorisation](/guides/transactions/incremental-authorisation):** Increase the authorised amount of a transaction. For example, if the price of goods has changed.
* **[Void](/guides/transactions/void):** Cancel a transaction that has been authorised, but not captured.


To modify a transaction, you'll need to supply its associated `systemTransactionId` as part of the URL path. If your request is successful, you'll receive a response containing a new `systemTransactionId` that can be used for tracking and reconciliation purposes. Depending on your modification, the transaction's state might change. For example, if you capture a transaction, `"state": "Approved"` will be updated to `"state": "Captured"`.

You should always supply the first `systemTransactionId` that was returned for the authorisation or purchase that you're modifying. This ensures that the correct one is referenced for any subsequent operations.