I am wiring a room with a 20 amp circuit. All of the receptacles are rated at 20 amps and I am running it all with 12 gauge wire. My question is when it comes to the switch for the ceiling fan/light, does the switch need to be rated 20 amp or can I use a 15 amp switch as the fixture probably doesn't even use more than 4 or 5 amps max and will never change. The back of the 15 amp switch says it accepts 14 or 12 gauge wire. Thanks!

No, a 20 amp circuit requires a minimum of 20 amp rated devices.

Ok, but from some of your other posts, you have 15 amp receptacles on 20 amp circuits (as long as the whole circuit is wired with #12 wire), so why is a 15 amp switch different? Perhaps because a receptacle/switch may say 15A on it, but it's actually rated for 20 amp?

A 15 amp receptacle limits only a 15 amp plug to be inserted, thus limiting the load to 15 amps or less. A switch cannot do that. Anyone can come along and install larger lamps, add more fixtures, etc. and the switch can be overloaded.

You threw me off a bit when you said "a 20 amp circuit requires a minimum of 20 amp rated devices", cause I was reading all over the place that you could put a 15 amp device on a 20 amp circuit.

Yep makes sense, so I think I will take out the 20 amp receptacles and replace those with 15 amp receptacles and then make my switch a 20 amp switch - and I should be good to go. Thanks for the advice!

Yes, my wording was a bit confusing, I should have used the word "switch" and not " devices, since 15 amp receptacle can be on a 20 amp circuit.

Sorry for the confusion.

Leave the 20 amp receptacles and only buy the one 20 amp switch. This will save you some work and money.