The Illinois Petition for Letters of Administration is a legal document used when an individual dies without leaving a will. This document is filed with the local probate court by the surviving spouse, children, or other close relative of the deceased. It is used to appoint someone as the personal representative of the estate and to grant them the authority to manage the assets of the deceased. There are two types of Illinois Petition for Letters of Administration: Regular and Formal Administration. Regular Administration is used when the estate is not complicated and the assets are of a modest value. Formal Administration is used when the estate is more complicated or the value of the assets is high.