We've had our house's foundation leveled, but our back door's deadbolt will not lock. How would I go about fixing this?

How far off is it? Will it lock of the door lock isn't engauged or does it just seem way off?

Does the door close OK? Does the key lock set engage its striker correctly?

If these are OK, relocate the striker for the dead bolt. U will have to fill the screw holes in jamb. Use a small piece of wood with glue. If the striker is installed correctly, the screws will be long enough to reach the stud.

Chuck

Well properly, if the house is "settled" it means your foundation and/or the floor is no longer level and/or the house has shifted.

Having a professional investigate and find out why, idea you would level the house if it is not level.