Welcome to the Community space, @vitanovabookkeeping.
Yes, you can create a Journal Entry (JE) to remove your customer open balance. I'd be glad to walk you through the steps.
Before we begin, you'll want to consult with your accountant or visit our ProAdvisor page to look for one. This way, we can prevent messing up your book.
When you're ready, you can proceed to these steps:
- Sign in to your QuickBooks Online (QBO) account and navigate to the + New menu.
- Click Journal entry.
- In the first line, select Accounts Receivable A/R under the ACCOUNT column.
- Enter the amount under the DEBITS column and select the name of the customer name under the NAME column.
- In the next line, select an offset account (usually an Expense account) and enter the amount under the CREDIT column.

- Once done, select Save and close or Save and new.
You can also see this article for more details (though the steps is for QuickBooks Desktop (QBDT), the workflow also applies to QBO): Write off customer and vendor balances.
You might also want to check this link for guidance in case you need to link a deposit to an invoice: How to link a deposit to an invoice.
Let me know in your reply if you have any other concerns managing your customers and invoices. I'll be around to help you out. Keep safe!