Sync Error | This expense line cannot be billable

What does this mean?

This error indicates that the user has toggled "billable" to Yes, but did not select a Customer/Job.

Keep in mind that "billable" is an accounting term and is basically a question of, "can I charge a customer for this expense/associate it with this specific job for them to pay later?"

How to resolve:

You will need to either select a Customer/Job, or toggle "Billable" to No.