How do I reflect a previous month's payment on a new invoice?

Hello there, @boffinelley. 

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Thanks for asking us here in the Community. At the moment, the option to reflect a previous month's payment on a new invoice. 

However, you'll want to turn on the Account Summary feature to reflect the past balance to a current invoice. Here's how: 

1. Click the Gear icon, then choose Custom Form Styles.
2. Click Edit to open the template, then the Content tab.
3. Click the Content area on the right pane.
4. Put a checkmark in the Show on the invoice field.
5. Click Save and Exit.

I'm also adding articles on creating and applying for credits in QBO should you need to reflect a credit for your customers.

I'd be here to help you more with your additional concerns. Take care!