It's nice to see you here, @Gina T,
I can help you further with recording your invoices and pre-payments. If you want to mark the invoices as unpaid, you can simply remove the payment from it. This way, you don't have to delete the invoice and recreate it.
To delete a payment, follow the steps below:
Also, to record a pre-payment, you may set up a retainer deposit so you can apply it at a later time. Here are the steps to do that:
Step 1: Create a trust liability bank account: (optional)
Step 2: Create a trust liability account:
Step 3: Create a product or service item that uses the trust liability account
To get more information about this, see this article: Record a retainer or deposit
If you have other questions about this, please let me know in the comment below. I'll be right here to share some more information about sales and payments. Have a nice day!