You can run a Void when you need to cancel a sale that has not been settled yet or an authOnly. To void a sale you need to provide the SaleGuid or SaleReferenceNumber that you received when you ran the Sale. To void an authOnly you need to provide the AuthOnlyGuid or AuthOnlyReferenceNumber that you received when you ran the authOnly.
This endpoint creates a void.
Voiding a Sale Containing Enhanced Data
If you need to void a sale originally created with values in the enhanced data object you will need to include the enhanced data object in the void request as well.