READER Q & A:

There’s no registration of handguns in Washington, but does that mean I, as an individual gun owner, can post it on Craigslist? Do I have to report the sale in any way?

There is no federal law requiring you to report anything, I am not sure about state law. As long as the buyer is legally allowed to own firearms, you should be fine. You may want to look into whether or not your state would hold you liable if he turns out to be a felon or other prohibited person.