What Requires a Permit
In general, permits are required for structural work, additions, new construction, electrical and plumbing modifications, HVAC changes, and work that alters egress or occupancy.
Cosmetic work such as painting, flooring replacement, and cabinet swaps typically does not. The line is not always obvious, and it varies by jurisdiction.
Working without a required permit creates real problems at resale, can void insurance coverage, and may require removing completed work. It is not worth the shortcut.