First off this is not a legal guide and remember that every locality is different. Even if you moved 50 miles within the same state you may find that rules are very different based on State, County, City Permit rules. The only way to know exactly when or why a Permit is required is to call the Building Official for your specific location and ask to speak to the office that performs electrical inspections.
So, when is an electrical permit normally required?
Electrical permits are normally required for all new construction. This means when a home is originally built and when additions and alterations to the original electrical plan have been made such as adding an addition to your home or remodeling and reconfiguring a bathroom or kitchen.
Normally permits are not required when wiring appliances such as a light fixture, ceiling fan, Like-in-kind replacement of a single circuit breaker, fuse, lamp, snap switch, receptacle outlet, household appliance, heating element, identical fluorescent ballast, relay, timer, motor starter, a similar control component, or a single 10 horsepower or smaller motor.
A basic rule of thumb is if you are adding wire in the wall you will need a permit and inspection.
Why should you apply for a Permit?
Permits will require an inspection after the work is completed and often during the process.
Although you can bet the law in your area is written to remove all liability from any inspection performed by a local official or person qualified to perform an inspection the added benefit of having an inspection will increase the probability the work will get completed correctly.
Although Fines for unpermitted work are also a problem there is usually a resolution process.
Can I do the work or must I hire a professional?
Most locations allow the home owner to perform electrical work in their home if they obtain a permit and pass an inspection. If you feel that you can not perform the work due to lack of knowledge or other reason then hiring a professional licensed electrician directly is your best bet.
If you hire an electrical contractor, be sure he or she is properly licensed. Check your contractor’s license and whether that contractor has past violations
Who Buys The Permit?
Normally if you do the work then you buy the permit.
If you hire someone to do the work then they must buy the permit.
If you hire a contractor that is not a licensed electrician or a general contractor that is not subcontracting the work to a licensed electrician they may try to get you to purchase the permit. Be careful when you are approached by a contractor to do this. Often it is a way to get around the law on paper but can leave you with work that can not be insured on your home insurance.
Final Note
Whether you are performing the work yourself or hiring a professional take an hour to call your local building official and inquire about electrical permits for any work you need completed.
You can also ask about the licensing of your contractor and if any claims have been filed against them in the past.