815 ILCS 105/3

All promissory notes, bonds, due bills and other instruments in writing, made or to be made, by any person, body politic or corporate, whereby such person promises or agrees to pay any sum of money or articles of personal property, or any sum of money in personal property, or acknowledges any sum of money or article of personal property to be due to any other person, shall be taken to be due and payable, and the sum of money or article of personal property therein mentioned shall, by virtue thereof, be due and payable as therein expressed.