Cancelling in Payment Calendar
Cancellation of a posted payment is the same as in the case of financial leasing - services, see https://iao.atlassian.net/wiki/x/xYDPAQ
If Financing is VAT=Y:
Before you can cancel the payment, you must first unsettle the posted financed VAT (customer entry of type "empty") that settles the initial VAT invoice.
A payment with a settled customer entry cannot be cancelled, the cancellation is terminated by the error message "Entry Customer Ledger Entry % cannot be cancelled because the item is applied by another entry or has been changed by a batch job".
When a payment is cancelled, the following reverse documents are posted:
Credit memo - it is automatically settled with the invoice (original posted payment), if it is open
internal document - reverse of posted VAT settlement from payment calendar; The reverse is automatically applied to the reversed VAT settlement entry (customer entry type "empty")