Hello there, @629786.

You need to select an account to get past this warning message and save the invoice successfully. Let me show you how: 

1. On the left pane, select + New. 
2. Under CUSTOMERS, click Invoice. 
3. Enter the transaction information, including the deposit amount. 
4. Click anywhere to view the Deposit to field.
5. Select the Deposit to drop-down and select an account.
6. Click Save and close. 

For additional reference, I've attached some links for options to receive and categorize customer payments in QuickBooks Online: 

• Record invoice payments

• How to let customers pay their invoices online

Let us know how I can help you further by clicking the Reply button below. Have a great day ahead.