What electrical work requires a permit?

Any time you make modifications/additions to facility wiring. Changing an outlet probably doesn't require a permit (check with local authorities beforehand), but it's best to have a licensed electrician do the work for insurance purposes, especially if you don't know what you're doing. That doesn't mean they'll do good work as I've seen electricians do shoddy work that was outright dangerous. I make it a point to always check their work and have them fix it if done wrong or poorly.

depends on country, state, county...