File an annual report for a Corporation, Not-for-Profit, or Limited Liability Company online. Incorporate a business or terminate an LLC.You'll need to register your business with the state, prepare internal corporate documents, appoint company directors, and issue stock. Form REG-1 is available as a fillable and savable pdf on our website at tax.illinois.gov. To form a corporation in Illinois, one of the first legal steps you need to take is filing articles pertaining to incorporating in Illinois. You must register your business entity with the proper government agency, once the most appropriate business entity is determined. The main requirement is to create and file articles of incorporation, which include details about the organization.