The legal requirements for starting a business come down to five things: choosing and registering an entity, getting an EIN, handling state and local licensing, setting up tax registrations, and keeping up with ongoing compliance filings. Those who have come across this article while searching for the legal requirements to start a business likely have a product or an idea in mind. In the US, the norm is to form an LLC rather than a corporation. Put in any state tax registrations where you have employees or nexus. Common Mistakes Founders Make With Legal SetupWhen it comes to the legal side of things, founders tend to make the same mistakes over and over again.