Sign off sheet for a sub working for a contractor - YESDepends on the contract and state in which you do business. I am not required to give any warranty on my services. I do, but I am not required. I obviously have to do what I have been contracted to do, but other than that I can give a tail light warranty if I so wished.
For a contractor working for a homeowner - NO
Where I come from the warranty has to be stated in the contract, by law and the minimum (if I am correct) for new construction is 1 year. My point about a sign off sheet is that it is moot and likely to be used as an attempt for the contractor to try to get out of making corrections when faults are found later. To each his own. If I know I did a complete job with top-quality work then I have no problem with asking for my final payment without asking for a sign off sheet.
Do I really have to re-post many of the posts where contractors on this forum call their customers liars, crooks, ignorant, scam artists, cheap, etc.?