SIMA notes that a snow contractor can be named in a slip-and-fall suit even where the refreeze was not theirs to treat, and its warning is blunt: unclear or missing documentation will almost certainly cost you if a lawsuit is filed.
The Western Trade Center RFP attaches a site plan of its own as an exhibit, with the areas where snow may be piled marked on it. Keep your own plan for every lot, along with these records.
The first item on SIMA's list is the drawing. For a suburban medical-office plaza, that is the paved lot of 48,000 sq ft, 2,400 sq ft of walks your crew clears by hand, and the 6,200 sq ft where the piles are allowed to go. Marked before the first storm, it shows what you agreed to clear and what you did not.
SurfaceMeasure's Snow Removal mode builds it from an address. Trace the lot and the walks as their own sections on satellite imagery, and the quote lists each one's square footage with the satellite view of what you traced, priced per push, salt and season at your rate. Send it to the property manager, and keep it with the contract as the site map for the season. The visit log on storm nights is a separate record, and you keep it yourself.