A letter of instruction is an estate planning tool that can be very helpful in the administration of your estate. Notify Bank of America.We'll ask you for the deceased customer's full legal name and Social Security number to identify their accounts. The Probate Court can assist with small estates petitions, wills on deposit and caveats. Trust administration involves handling assets titled in the name of the living trust. The successor trustee must find out what the trust owns. Letter of Instruction. This guide is designed to teach you how to write a letter of instruction for heirs, or anyone else who may benefit from a little more direction. All documents posted below in PDF format must be filed with the court in PDF format. Remember to sign and date your letter.