If the fuel tank was kept full, then there should be no issue using the fuel. The biggest problem comes from ethanol in the fuel absorbing water from the air. With a full tank of gas, there's no real room for air to be there, so little to no absorption occurs.
If the tank was not quite as full as you thought (either completely dry or completely full is the best way to store a vehicle), there are products you can purchase which will help the fuel. As said in the other answer, it is a good idea to get fresh fuel into the tank before you run it too much. Cutting the fuel with fresh will give you good results while getting rid of the old fuel safely. If there was only a 1/4 tank (or around that) without fuel stabilizer, you'd want drain the tank and run completely fresh gas in it. If you are in a part of the world which doesn't use an ethanol blend, you wouldn't have much to worry about. I've seen old, non-ethanol fuel, run without issue ... And I'm talking old fuel here.
Fuel can stay good for a long period of time if it can't absorb water. Fuel stabilizer can help if used prior to the vehicle sitting still, but does little if anything after the fact. If the fuel has absorbed water, there is a chance of corrosion and sediment which can plug fuel filters and injectors.