Hello there, @mbell19.

Allow me to jump in and help you write off bad debt in QuickBooks Online (QBO).

There are different options on how to close an open invoice, however, the process depends on the scenarios.
 

First, once an invoice becomes non-collectible, you'll need to write it off and declare it as a bad debt to clear the invoice out of your accounts receivable and reduce your net profit by its amount. 

Here's how:

Create a bad debts expense account. 

1. Click the gear icon. 
2. Choose Chart of accounts.
3. From the Account type dropdown, hit Bad debts.
4. In the Name field, enter Bad debts.
5. Tap Save and Close.

Then, create a bad debt item.
 

1. Tap the gear icon.
2. Choose Products and Services.
3. At the upper right, hit New, and then Non-inventory.
4. In the Name field, enter Bad debts.
5. Tick Save and Close.

After that, create a credit memo for the bad debt.

1. Hit +New.
2. Tap Credit memo.
3. Choose the customer from the Customer dropdown.
4. In the Product/Service section, click Bad debts.
5. In the Amount column, enter the amount you want to write off.
6. In the Message displayed on statement box, Enter "Bad debt."
7. Tick Save and close.

Lastly, apply the credit memo to the invoice.
 

1. Choose +New.
2. Under Customers, tap Receive payment.
3. From the Customer dropdown, select the customer.
4. From the Outstanding Transactions section, tap the invoice.
5. Find the Credits section, and click the credit memo.
6. Hit Save and close.

You can check this article for detailed steps on how to write off bad debt.

Once done, you can now run the Accounts Receivable Aging report again. See this article, for more information: How to get your Aging Reports to match.
 

Additionally, you can visit the following write-up: Sales and customers. This will provide you with links on how to manage your company income as well as resources about other customer-related concerns.

I also recommend consulting an accountant if you’re not familiar with the process to ensure your books are accurate.

Please know that I'm just a post away if you have any other concerns about the Invoice in QBO. Wishing you and your business continued success.