"A letter of last instruction is a document that outlines funeral planning processes and arrangements. There are key items a letter of last instructions should include to help loved ones navigate the legal and financial issues that follow death.This document typically lays out your legal documents, important personal and financial information, and funeral wishes, among other items. Get up to 10 copies of the death certificate. The Los Angeles estate planning attorneys at Schomer Law Group, APC explain how a letter of instruction might fit into your estate plan. A letter of last instruction is an organized way for you to give your family all the facts about your finances—and have a basic tool for your own. Letter of Instruction. Used only if there is a beneficiary named on the account. To start the process of obtaining a letter of administration, you must fill out Form DE150. The completed form DE150 should then be submitted to the probate court in the county in which the deceased resided in at the time of death.