Open Payments. It only closes debts. Debts are created by sales and purchases. Payments settle them.

Customer pays you: pick the customer, choose Received (money in). What they owe goes down, your cash goes up.

You pay a vendor: pick the vendor, choose Paid (money out). What you owe goes down, your cash goes down.

If a sale was marked Collected in full, you need no payment for it. Balance checks later prove the cash ended where you said.