Hope this helps - I'm new to X3 so I have a theory that if I help someone, someday it may come back :)

Voiding Payments

If you have not posted the payment (validated) to the Bank, then you can delete the payment using the Delete button in the Payment / receipts entry function.

If you have posted the payment to the Bank, then you must select Accounting cancellation under Options in the Right panel to reverse the journal entry.

- Once reversed, you can make changes to the payment and re-validate or click Delete to delete the payment.

- The reversing journal created from the Accounting cancellation function has a description that references the original payment journal. You can use this as a trace for the payment deletion for posted payments.

If the Accounting Cancellation option Ghosted it needs to be enabled.