1. Corporate Name: 2. To withdraw your foreign corporation in Illinois, you must complete and submit BCA 13.45, Application for Withdrawal and Final Report form in duplicate.Corporations must complete Form IL-1120. Do not send a computer printout with line numbers and dollar amounts attached to a blank copy of the return. The BCA 13.45 Application for Withdrawal and Final report is required when your company is no longer doing business in Illinois. Who must file Form IL-1120-ST? You must file Form IL-1120-ST if you are a small business corporation ("S corporation"), as defined in Internal Revenue Code. If you have decided to stop doing business, here's what you need to know about dissolution vs withdrawal for your corporation of LLC.