Welcome to the Community. I can provide steps on handling payments from the last month to the total invoice amount for this month in QuickBooks Online (QBO).
Before we start, may I ask if this is an overpayment from the last month? If so, please note that QuickBooks will automatically generate a credit for the excess payments. In this case, we can apply the credit to this month's open invoice when receiving payments:
- Sign in to your QBO account.
- Click the + New icon and select Receive Payment.
- Select the specific customer.
- The total invoice for this month will appear in the Outstanding Transactions section, and the credit for the last month's payments will appear in the Credits section.
- Put a checkmark in this month's open invoice and select the credits last month to apply.
For more information about applying credit to an invoice, here's an article for your guide: Handle customer overpayments in QBO.
On the other hand, if the payments from last month have not been applied to any invoice, we can create a bank deposit and apply it to the open invoice for this month. For a step-by-step process, please refer to this article: Link a bank deposit to an invoice in QBO.
Furthermore, we can run reports to get insights into your business financials: Run reports in QBO.
I'm always here if you require assistance subtracting the paid amount from the last month from the total invoice this month. Have a good one.
