When editing a payment form, you can add a setup or additional fee by scrolling down to the Amount section and activating Additional Fee.

Add a name to your fee and choose whether the fee is a % of the amount charged or a fixed amount.
When editing a payment form, you can add a setup or additional fee by scrolling down to the Amount section and activating Additional Fee.
Add a name to your fee and choose whether the fee is a % of the amount charged or a fixed amount.