In most cases, it is perfectly legitimate to simply insert a lump sum amount owed in the mechanic's lien form and leave it at that. There are some minor instances in which states require an itemization, but the majority of states do not do so. As an example, your mechanic's lien might read: “The amount claimed is $ 17,432.00, plus interest at the legal rate from an after July 15, 2008.”
But should you add more detail? In my opinion, you should. The more detailed your explanation, the more chance of being paid. If a person has a genuine uncertainty as to your claim, there will be a referral to write you a check. Alternately, if you lay out the various amounts, they might be more willing to pay the undputed amounts.
A simple way to itemize the amounts is found in many of the standard mechanic's liens on the internet. Here is an example.
Amount Owing: As of the date below, the sum of:
$ ___________, itemized:
Total Owed / Billed on Base Contract for Entire Job:
Less All Payments (Invoices attached-Optional):
If you want to go further, you can do a breakdown of the amounts owed on the base contract, and then list every change order, by number, that has not been paid, with a brief description.
Alternately, you can simply attach one or more invoices which lay it out, with more particularity. This is especially the case with signed change orders – include them. But be careful about attaching too much paper, because each page is charged separately by the recorder. Good luck.