There's multiple ways to mark a sales quick entry as paid in Sage Accounting, depending on how you process your transactions.

Sales quick entry invoice

• Record a manual customer receipt from banking
• Use bank feeds or imported bank transactions to create a customer receipt
• Allocate a payment on account or credit note to an existing quick entry invoice

Sales quick entry credit note

• Record a manual customer refund from banking
• Use bank feeds or imported bank transactions to create a customer receipt
• Allocate the credit note to an existing invoice