Complete Illinois Department of Revenue (ST-556, RUT-25 or RUT-75) tax form and a check payable to IDOR. An Illinois boat bill of sale is a form that transfers a boat from seller to buyer for an agreedupon price.How do I fill this out? Complete your Illinois bill of sale for selling a boat here. Our bills of sale meet the state requirements. Copy of Bill of Sale or Purchase Agreement; Check or money order payable to Dept of Revenue for tax amount due.