How often does my dog need a rabies shot?

Legally you can select either 1 or 3 year rabies shot. If you select the 3 year, you want to make sure you keep the paperwork. Otherwise your vet can reprint out the info for you too ;)

It also depends on the dog's age and the laws of your municipality. In the places I've lived, if a rabies vaccine is given to a dog less than a year old, it is considered a 1-year vaccine. When the dog is given booster shoots (after a year old) it is good for 3 years. An exception to this is if the dog's first rabies vax is given when he or she is over a year old, it is only good for 1 year.

The law may be different where you live; in some places, the longest a rabies vax is good for is 2 years. Regardless, it's not a one-time thing. Your dog will need (legally) to have rabies boosters throughout his life.

And, btw, the actual vaccine that is given is the same product whether it is considered a 1-year or a 3-year vaccine.

Rabies is considered to be a core vaccine for dogs and should be administered every 1 to 3 years

I agree with Walt and Serina. For others interested in the replies to this question: If you are not sure of the dog's vaccination history, you can always have your vet perform a Titer test to determine if there are antibodies left from previous vaccinations. Depending on result of the test, you can decide which vaccination your dog should get - 1 or 3 year.