You (or the purchaser or transferee) must complete Form CBS-1, Notice of Sale, Purchase, or Transfer of Business Assets. File your Illinois Business Registration Application online with MyTax Illinois.Go to Service. logo. This system allows you to form or register a Not-for-Profit, Domestic Corporation, or Limited Liability Company or terminate an LLC online. To organize an Illinois Limited Liability Company, complete and submit LLC-5.5, Articles of Organization. The due diligence process of acquiring a small business always starts with a comprehensive examination of all relevant financial documents. Free Consultation - Call (312) 889-8702 - The Castle Law Firm helps companies with business matters in Business and Franchise Law cases. This comprehensive guide explores the complexities of Illinois small business tax. From taxes and insurance, to business licenses and bank accounts, our guide will show you how to do it all and protect your personal assets in the process. Use tax may also apply if a business purchases taxable items from outofstate sellers.