Do I need to have a company to start selling on Amazon?

You do not need a company, but we recommend it.

You do not need to have a company to sell on Amazon. You can sign up as an individual.

A word of caution however: Things can get really messy if you are combining your personal and business transactions. If you decide to move forward as a sole proprietor, make sure to keep transactions separated on the banking side of things. 

Be sure to talk to your accountant to decide what is right for you.