Michigan law requires that all dogs four months of age or older be licensed.
A dog license is considered late if your animal is 5 months of age or older and you have owned the dog longer than 30 days. Dog licenses are discounted for senior citizens, and if your dog has been spayed or neutered (See fees here). To qualify for senior prices a person has to be 62 years old at the time of purchase and provide proof of age.
The fees through March 1, 2013 range from $6-26. After March 1, the costs of licenses doubles.