How to close invoice with small balance left?

I can help you with that, usernatasha.

You can write off bad debt for the remaining balance. This way, you'll be able to close the open invoice and zero out the $0.91 customer balance. I'll show you how.

First, you'll have to create an expense account for bad debts:
 

1. Select Accounting from the sidebar menu, then go to Chart of Accounts.
2. Click New to create a new account.
3. From the Account Type drop-down menu, select Expenses.
4. From the Detail Type dropdown menu, choose Bad debts.
5. In the Name field, enter “Bad debts.”
6. Hit Save and Close.

Then, create a non-inventory item that will hold the bad debt:
 

1. Select Sales from the sidebar menu.
2. Go to the Products and Services tab.
3. Click New, and then choose Non-inventory.
4. In the Name field, enter “Bad debts.”
5. From the Income account drop-down, select Bad debts.
6. Hit Save and Close.

Once done, you'll need to create a credit memo and apply it to the invoice you want to close. The steps are highlighted in the Steps 4-5 section of this article: Write off bad debt. It also contains the procedures on how to run reports for the uncollectible receivables.

In addition, I've attached a link that will help you manage your invoice, sales receipt, and other sales forms in QuickBooks: Sales transactions.

Do you have any other questions in mind? Feel free to post them in the comment section. I'll be more than happy to help you again.