Does an Outlet in a Soffit Need to Be GFCI Protected?
Yes. A receptacle mounted in a soffit is outdoors, and 210.8(A)(3) requires GFCI protection for all receptacles installed outdoors in dwelling units. The soffit being tucked under an overhang and protected from direct rain does not move it indoors. It is on the exterior of the building, and that is the test the code applies.
The GFCI requirement
Section 210.8(A) in the 2023 NEC requires ground fault circuit interrupter protection for personnel for receptacles rated 150 volts to ground or less and 50 amperes or less installed in the locations listed, and 210.8(A)(3) is outdoors. There is no exception for a receptacle under an eave, in a soffit, on a covered porch, or inside a screened enclosure.
The 2020 and later codes removed the old exception for receptacles that were not readily accessible and supplied a fixed electric snow melting or deicing equipment. That exception is where the older soffit argument came from, and it is gone for general purpose outlets. Section 210.8 also requires the GFCI device to be readily accessible, which for a soffit receptacle at 9 or 10 feet in the air means the protection almost always has to be a GFCI breaker at the panel or an upstream GFCI receptacle at a reachable height.
Weather resistant and cover requirements
Section 406.9(A) and (B) govern receptacles in damp and wet locations. A soffit location is at minimum a damp location, and where it can be reached by wind driven rain it is a wet location. Section 406.9(A) requires an enclosure for a damp location that is weatherproof when the attachment plug cap is removed. Section 406.9(B)(1) requires a wet location receptacle to have an enclosure that is weatherproof whether or not the plug is inserted, which is the listed while in use cover, sometimes called a bubble cover.
Section 406.9(A) and (B) also require the receptacle itself to be a listed weather resistant type, marked WR, in both damp and wet locations. That marking is separate from the cover, and an ordinary indoor receptacle behind an in use cover does not satisfy it.
Holiday lighting is the usual reason a soffit receptacle exists, and cord caps stay plugged in for six weeks straight in freezing rain. That is exactly the scenario the while in use cover was written for.
The rest of the install
Section 210.52(E)(1) requires at least one receptacle outlet at the front and back of a dwelling, accessible from grade and not more than 6 feet 6 inches above grade. A soffit receptacle does not satisfy that requirement because of the height limit, so it is an addition rather than a substitute.
Article 314 governs the box. Use a box listed for damp or wet location use, mount it so water does not collect inside, and support it per 314.23. If you are feeding it with NM cable from the attic, the cable stays inside the building envelope and the box has to be sealed where it penetrates the soffit board.
Section 210.12 is the last piece. Outdoor receptacles in dwellings are covered by the 2023 expansion of AFCI requirements in some editions and jurisdictions, so a soffit outlet may need both AFCI and GFCI protection. A dual function breaker handles both in one device and is usually cheaper than two separate solutions.
A switched soffit circuit controlled from inside the house is a nice touch for holiday lighting and is entirely permitted, as long as the switch does not defeat the GFCI protection ahead of it.