We are using Invoice Ninja - v4.0.1 | White labeled and Stripe for the payment gateway.
When we create an invoice for a client and they pay with a credit card, there are charged a Surcharge which is added to the invoice. Client pays the invoice but when we refund the amount, the invoice becomes Unpaid but the Surchange is still on the invoice. When the client decides to pay using a credit card again, the invoices adds another line Surcharge entry in the invoice and therefore increases the amount due.
This appears to be a bug…