I use Sum Up set as a Merchant account and my client gets a statement from Sumup showing the amount received less the bank charges so I post the gross amount received into Sumup by creating a transaction and creating a customer invoice and then a payment for the amount deducted by creating a supplier invoice (I call both accounts Sumup as customer and supplier) and then reconcile the 2 created transactions with the bank receipt taking the merchant account back to zero - does that make sense?