You might not be sure whether or not you’ll need a permit for your next project. Of course the best resource to help you answer that question for your specific project is to call your local municipality. Believe it or not, many building inspectors are happy to discuss permitting issues with anonymous callers as a way to ward off future code violations.
If you’re repainting the bathroom or living room, you do not need a permit. If you’re remodeling your bathroom, you probably only need an electrical permit, and plumbing permit.
You would need a building permit if you are removing structural beams or moving or resizing a window. In a standard bathroom remodel you are probably leaving the walls alone, and perhaps replacing, but not moving or resizing a window.
So, what it often comes down to is what kind of remodel you are really doing. If all you are doing is a little lipstick changes, ie. tile, fixtures, paint, you’re probably safe. But any changes with the bones including plumbing, wiring, and walls then definitely you do.
Look at it this way, when you don't have something inspected you risk much more than a fine or a slap on the wrist if something goes wrong. I have everything inspected no matter how small… it is better to be safe then lose everything because of work not done to codes.
Remember, no job is that small and that safe that you can take the chance with the lives of those you love. Building codes are developed, changed, and enforced for one main reason - safety.