I know it's important to ensure your customer is billed with the correct amount, desertcoolingsys. I'd be delighted to share the steps to do this.
You can use the Progress Invoice feature in QuickBooks Online. This way, you can bill your customer for partial payments instead of asking for full payment.
Here's how to turn on the feature:
- Go to the Gear icon and then click Account and settings.
- Choose the Sales tab.
- From the Progress Invoicing section, select Edit.
- Turn on the Create multiple partial invoices from a single estimate button.

- Once finished, select Save and then Done.
After that, you can split an estimate into as many invoices as you need. For more information about the process, please see this article: Set up and Send Progress Invoices.
Additionally, I've also added this article that'll serve as your guide in managing invoice payments: Record Invoice Payments. It also includes steps on how you can enter a partial payment from your customers.
Feel free to post here again if you need further assistance in managing your sales transactions in QuickBooks Online, desertcoolingsys. I'm always here to help you out.