Accounting for Warranty Work

What is the proper/professional way to account for work done under warranty?

For instance the other day I had a no-start condition for a unit I had fixed a couple months back. Go out to find it was a non-conductive fuse in a holder that I had installed on the last trip.

I fixed it and said have a nice day.

But if I was going to run this business like a business I should be accounting for this just like any other repair and have the work order/invoice get paid from an expense category...

Accounting for Warranty Work

Accounting for Warranty Work