What needs a permit, and what genuinely does not
A practical line between cosmetic work you can just do and work that will come back to bite you.
The working rule
If the work touches structure, electrical, plumbing, mechanical, the roof, windows, doors, or the exterior envelope, assume it needs a permit. If it is purely cosmetic and reversible, it generally does not.
That rule gets you to the right answer most of the time. The exceptions are where people get into trouble, and they cluster in predictable places.
Generally does not need a permit
Painting, inside or out. Flooring replacement over an existing subfloor. Cabinet and countertop replacement where plumbing and electrical are not moved. Fixture swaps in the same location. Landscaping that does not involve tree removal, drainage changes, or impervious surface.
Note the qualifiers. Swapping a sink in place is different from moving it four feet. Landscaping is different from removing a protected tree, which several jurisdictions permit separately and take seriously.
Generally does need a permit, including some that surprise people
Water heater replacement. This one catches homeowners constantly because it feels like an appliance swap. It is a plumbing and often electrical or gas permit.
Air conditioning changeouts. Same reasoning.
Re-roofing, and repairs above the jurisdiction's threshold. Window and door replacement, including like-for-like.
Electrical panel upgrades, added circuits, and anything in a wall. Water heater relocations, re-pipes, and sewer line work.
Fences, sheds above the size threshold, driveways, pools, and screen enclosures. These are the ones people assume are trivial and that get denied over setbacks and easements more than any other residential category.
Why skipping it costs more than doing it
Unpermitted work does not stay invisible. It surfaces at sale, at refinance, when a neighbor complains, when an insurance claim is investigated, or when a future permit application triggers a look at the property record.
At that point you are paying the original permit cost, plus a penalty multiplier, plus a design professional to document existing conditions, plus possibly opening finished walls. The arithmetic is never favorable.
Insurance is the underrated risk. A claim involving unpermitted electrical or roofing work is exactly the kind of thing a carrier examines closely.
The free way to check
Ask the building department directly, or ask us. Describing a scope and getting a yes or no takes a few minutes and neither of us charges for it. The expensive version of this question is the one you answer by assuming.