How can I release preauthorized funds after a transaction is cancelled?

Once a transaction has been cancelled, there are no outstanding authorization holds on Adyen’s end. 

As the authorized amount was not captured, it was automatically released back to the customer. The timing of this release depends on the customer’s bank and how promptly they update pending charges. The customer may also contact their bank directly to request that the pending charge be corrected.

Here, you can see how a Cancelled authorization is reflected in the Customer Area: