For LLCs, it is highly recommended to have an Operating Agreement. This is an internal document that sets the rules for how your LLC is run, including member roles, decision-making, profit distribution, and other important business operations. Montana law does not require you to file this document with the state; however, having one helps protect your company and clarify its operations.
For corporations, bylaws serve a similar purpose by establishing the internal rules and procedures. While corporations usually need bylaws, these are not filed with the state either—they are kept as internal records to help protect your legal standing.