[The title of this thread has been edited from the original: adding a "convenience fee" line item]
It would be great to be able to send and invoice with a convenience fee percentage.
A lot of locations charge a convenience fee for taking a credit card. This would give customers the option to send in a payment or to use a card. For the merchant it would help offset the costs of accepting credit cards.
It sounds like you're referring to adding a surcharge to your Invoices and payments.
While we can't advise on surcharges, here is a thread where other sellers have written about what they've done to add a convenience fee, or surcharge to their sales.
We suggest talking to a tax or legal professional for guidance on whether surcharges are permitted in your area. If decide to apply a surcharge or convenience fee, it is your responsibility to meet all legal and card network requirements. You can learn more about surcharges here.