How to post late charges on over due accounts

I'll provide the two options on how to post late charges on overdue customer accounts in QuickBooks Online (QBO), @dfiddie.

If you want to manually include late charges on existing and new invoices, I'd first suggest creating a service item. This way, you can add a standard fee with a clear and detailed description to the transactions. I'll guide you how. 

1. Go to Sales from the left menu.
2. Select Products and Services.
3. Choose New.
4. Click Service.
5. Enter the fee's name, such as Late Charges On Overdue Accounts. 
6. Fill out the rest of the necessary fields. 
7. Hit Save and close.

The screenshot below shows you the last three steps. 

Once done, let's add the late charges to the invoices, whether you've already sent them or not. For the detailed instructions, see Step 2 through this article: Add Service Fees Manually To Invoices. 

If you want to auto-apply late charges on future overdue invoices, let's turn on the Late fees feature in the settings. This way, you set the charge amount and when to apply it after the due date. The program will automatically add the fee as a line item under Product/Service on the invoice. Please log in to your QBO account as a Master or Company Admin before performing the steps below. 

1. Go to the Settings (Gear) icon at the upper right.
2. Select Account and Settings under Your Company. 
3. Go to Sales from the left menu. 
4. Click Late fees.
5. Check the Default charge applied to overdue invoices box. 
6. Specify the Type, Amount, Frequency, Grace period, and the sales tax implication.
7. Click Save. 
8. Hit Done.

See the screenshot below to show you the last six steps. 

After that, let's go to your overdue customer accounts. Just select the Customers tab from the Sales menu. Then, open the customer's profile, choose Late Fees, and click Customize. From there, you can set a custom fee for them. View the screenshot below for your visual reference. 

To learn more about the process above, check out this article: Set Up Automatic Late Fees To Invoices. It also has answers to the frequently asked questions about using this feature in QBO.  

I recommend running the Account QuickReport of the Late Fee Income account. It helps you track the amount of the total fees you’ve collected within a specific period. Just go to the Chart of Accounts menu and enter the name in the Search box. Then, click Run report from the Action column. I've attached a screenshot below on how it looks like in QBO. 

I'm just a comment away if you need anything else. Keep safe always, @dfiddie.