I'm glad you reached out to us, francesca-procto.

You can either record the payment as Deposit or Receive Payment for the monthly partial amount. The steps on how to do both ways are outlined below.

To create a Deposit:

1. Go to the +New icon.
2. Under Other, choose Bank deposit.
3. Fill in the necessary information.
4. Click Save and close.

Learn more about recording deposits in QBO through this article: Record and make Bank Deposits in QuickBooks Online.

To receive partial payment:

1. Go to the +New icon.
2. Under Customers, choose Receive Payment.
3. Enter the customer name. Select the invoice by putting a check mark.
4. On the Payment column, enter the partial payment amount (see screenshot).
5. Click Save and close.
   

The status of the invoice will automatically change to Partial. For a more in-depth information about invoice payment, you can refer to this article: Record customer payment in QuickBooks Online.

I'll be right here if you have further questions. Keep safe and have a good one.