Custom Fees are typically used by organizers who want to add a % or fixed fee amount to a specific item in the registration form e.g., sales tax item, or a blanket flat fee if someone adds a specific merchandise item.

To view if a participant is charged a Custom Fee,  you may Run Revenue Report. On the revenue report, a Custom Fee charge and refund will show under Column L: Transaction Type. Besides, you may also view the custom fee name under Column AC: Ledger description.
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Note: A participant will be able to view a Custom Fee charge or refund on their receipt and/or on their MyEvents account, under order review