"Letters of Office" is not really a letter. Working your way down, you'll fill out the name and address, as well as phone number.Who exactly is this "to? The Petition for Letters of Office asks the court to appoint a certain individual, called an Executor, to manage decedent's estate as identified in the Will. Edu or call 773.702. A letter of testamentary gives an estate's representative the legal authority to administer the deceased's estate. First you will need to obtain a copy of the death certificate to present to the court. No, a lawyer is not required. No letters of office are now outstanding on the decedent's estate, and no petition for letters is contemplated or pending in Illinois or in. You get letters of authority from the probate court, but first you need to have an estate opened up.