I also am frustrated that I spend much time unchecking the billable box.  I run a service oriented business and don't use P.O.'s but we have vendors (independent contractors).  I've noticed that the billable box is sometimes defaulted to check on Vendor Bills and sometimes not.  I haven't figured out if the default check is happening with the vendor, customer or item.  Each line of the vendor bill has an item and customer for report reasons.

Any insight would help.  Thank you.