Can a repair shop work on your car without a signature?

In most cases yes and no it depends. If the mechanic discovers a problem with your vehicle that adds to your original price you approved of then you are to sign for the extra work IF you want it done if not they are not permitted to work on your vehicle without your permission they are only to do what is on the reciept however if the extra problem poses a danger to the driver of the vehicle the mechanic might fix the problem and charge you but in any case they need your "ok" in order to work on the vehicle most shops do not even bother to have the owner sign the service recipt but i would recomend for legal purposes that u sign the service recipt no matter how major or minor the work to be done is because if a problem surfaces with the vehicle after it has been serviced and you did not sign the reciept you will have no proof that you did not cause the damage etc