@MrMoody - Yeah, the IRS tax exempt determination letter does more than tell you that you don’t have to pay taxes. It offers basic guidelines for how you are to conduct your operations.
For example, if you receive contributions it tells you that you have to report those contributions to your donors in the form of statements. It tells you about other record keeping requirements too.
I have a friend who started a nonprofit organization some time ago and that was one of the first pieces of business he took care of. He stores his letter in a safe place, too, because it’s a guarantee from the IRS that his organization is tax exempt.