Illinois Petition Probate Of Will and Letters Testamentary is a legal process used to validate a decedent’s Last Will and Testament in the state of Illinois. If the decedent left a valid Last Will and Testament, the Probate Court will issue Letters Testamentary to the Executor named in the will. This document grants the Executor the legal authority to administer the decedent's estate according to the terms of the Will. If the decedent did not leave a valid Will, the court will issue Letters of Administration to the estate’s Administrator, who is typically the decedent’s closest living relative. There are two types of Illinois Petition Probate Of Will and Letters Testamentary: Formal Administration and Informal Administration. Formal Administration is used when the decedent left a valid Last Will and Testament and the estate is worth more than $100,000. Informal Administration is used when the deceased left no valid will or the estate is worth less than $100,000. Both types of administration involve filing a Petition and other required documents with the Probate Court.