You have me to help you record your customer's invoice payment, sg13.
If you've received a deposit as their payment, we'll have to enter as Deposit. Then, use it as their invoice payment. I'll show you how:
Then, we'll have to link it to their open invoice:
You can also browse this article for more information when managing bank deposits: Record and make Bank Deposits in QuickBooks Online.
I'll be right here if you need help. Have a greay day!