You (or the purchaser or transferee) must complete Form CBS-1, Notice of Sale, Purchase, or Transfer of Business Assets. Step 1: Identify the business, business assets, or business property being sold or transferred.Browse 167 Chicago, IL business opportunities available on BizBuySell. To sell a business in Illinois, you'll need various legal documents, including a bill of sale, asset purchase agreement, and non-disclosure agreements. The due diligence process of acquiring a small business always starts with a comprehensive examination of all relevant financial documents. City of Chicago Account Number. Federal Employer Identification Number.