If you only know the exact price for an event afterward, you can create and send the correct invoices using the steps below.
Ensure you enter the correct price for each ticket type.
Click 'Bulk actions > Create invoices' in the top right corner of the event.
Select all participants for whom you want to create an invoice.
Choose the desired workflow.
Indicate whether you want to send the invoices immediately (otherwise, invoices will first be created as drafts).
Is the participation fee not fixed in advance? Then always make sure you select "invoice later" in your registration settings. This will prevent you from sending invoices with the wrong amount.
Incorrect amount invoiced
If incorrect amounts have already been invoiced for the event, it's important to credit the overcharged amount. You can do this by creating a credit note for the specific invoices. You can then offset the credit note against the original invoice.
The articles below explain how to do this:
Offsetting invoices against each other