Capital: Refers to money or assets, a city that is the seat of government for a region, uppercase letters, or something significant or praiseworth (as in “a capital idea”)
Capitol: Refers to capitol buildings where legislators meet
Grammar hack to remember: referring to the physical building is the ONLY time you use “capitol” with an O!
Good spelling is not just intuitive or inborn. You can train yourself to spell well! Just remember simple grammar hacks like this and you’ll be head and shoulders above everyone else who’s still making the same old mistakes!