You should have an LLC when selling on Amazon. For accounting, banking, and tax purposes, amongst other reasons.

I recommend using Bizee because it’s simple to use, and cheap. (link)

You can get your LLC in 1 business day for $299 + state filing fee.

Just click Form Your LLC and follow the steps. If you run a remote business, you’ll need to pick a state of formation. I chose Wyoming for my LLC. It’s popular amongst online business people because there’s no state tax, minimal annual fees, and minimal reporting requirements compared to other states.