Hello there, @gard898r.

I see this is your first question so let me take the time to welcome you here to the Intuit Community. Allow me to chime in for a moment and share some additional information about sorting your customers' names in QuickBooks Online (QBO).

The option to sort your customers' names according to their last name is unavailable at this time. However, as mentioned by @SouthernStacy, you can change their profile so it will show as the last name first as a workaround. Here's how:

1. Go to the Sales menu, then Customer tab.
2. Select the customer, then click the Edit button on the customer's profile.
3. Make sure to fill out the First and Last Name fields.
4. On the Display name as drop-down, select the option which starts with their last name. then click Save.

Just in case, you can also check out this article for future reference: How to edit customer information.

This should answer your question for today. Please let me know how it goes by leaving a comment on this thread. I'm always here if you have any additional concerns. Take care and have a great rest of the day!