I know this sounds sarcastic, and I mean no offense, but I am suprised by some of the responses I am reading here...
I don't leave materials behind (with the exception of the leftovers in a paint can (for touch up after someone scratches or dings a painted surface).
I certainly don't offer any credit or refund if we don't use all the materials purchased for a job. Heck, ussually we buy more than we need just so we don't have to stop and go back for supplies in case someone scews up. Return the overstock at the end of the project...
Aren't we "Contractors"???
I sell completed jobs. Often I subcontract a portion of a job out. I would be laughed at (not to mention extremely embarrassed) if I asked my subcontractors to refund any unused supplies (or leave them behind for the customer)...
Hey Electrician! I know you bid 1000ft roll of 12/2 wire for that project but only used 798 ft. Make sure you refund me the unused 202 ft or leave it behind for the customer... :w00t::w00t::w00t:
Hey Plumber! That toilet you installed didn't need the extra wax ring you included in the proposal, make sure you leave it behind or refund the value... :w00t::w00t::w00t:
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Insurance companies always expect up to 10% extra materials on submitted proposals. Anyone ever been asked to give back the unused materials or drop your price in the end???