Form CBS-1 must be filed with IDOR at least ten (10) business days prior to the date of sale or transfer. You (or the purchaser or transferee) must complete Form CBS-1, Notice of Sale, Purchase, or Transfer of Business Assets.Purchase a Certificate of Good Standing. A Certificate of Good Standing confirms compliance with the state of Illinois Business Services Department. This comprehensive guide explores the complexities of Illinois small business tax. I am going to show you how to fill out sales and use tax form st1 for illinois sales 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. Our free online guide for business owners covers Illinois sales tax registration, collecting, filing, due dates, nexus obligations, and more. This registration with the Department of Revenue gets you a tax I.D. number and tracks what kinds of taxes you owe the state. If you're buying or selling a vehicle, these documents are essential for completing the transfer of ownership.