Yes, you're absolutely right, golden2010.

Every time you create an invoice or sales receipt and add the retainer item with a negative amount, the balance of the liability account decreases. You can open it in the Chart of Accounts to see the result.

I got a sample below with a $10,000 prepayment. I deducted $1,000 on the first invoice of the customer. The remaining balance of the prepayment is now $9,000.

If there's anything that I can help you with your transactions, feel free to go back to this thread. Take care!