Hi there, @sales127.

Currently, the option to convert a sales receipt to an invoice is unavailable. You can delete your sales receipt so that you can make a receive payment on your invoice for this customer. Let me guide you how: 

1. On the left pane, select Sales then choose Customers from the drop-down list.
2. Find and select the customer's name. 
3. Under the Transaction List tab, locate the sales receipt. 
4. Click the drop-down arrow on the Action column and select the Delete option.

Once the sales receipt is deleted, you can now create the invoice in QuickBooks and record the customer payment. 

I've also included some articles for additional information about when to use a sales receipt and invoice, as well as how to create a template:

• Should I use an invoice or a sales receipt?

• New template format for Sales receipt and other transaction forms

If  you have any other questions, please don't hesitate to add a comment below. I'll be happy to help. Have a great weekend.