After a cancellation of a participant you can send a standard cancellation/invoice.
If you want you can create a text that will be printed above the payment summary.
Go to 'Basic Data' and choose for 'Cancellation/Invoice Text'.
The next screen will appear. Click 'New...' to create a new cancellation/invoice text.
Select the relevant conference in the dropdown list. The language of the conference will be selected automatically (the main language selected in Main Data). Create the cancellation/invoice text in the textbox.
After you've created the cancellation/invoice text, it will be printed above the payment summary.