For assistance in completing this request, please contact the Northern Funds Center at 800-595-9111 weekdays from a.m. An executor's letter of instruction serves as a roadmap, guiding the distribution of an estate according to the deceased's wishes.A letter of instruction is an important document used to help navigate the process of estate planning. Otherwise known as a letter of intent. "Letters of Office" is not really a letter. A letter of instruction is a document that guides a designated individual or entity on how to carry out specific actions or wishes after the author's demise. 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. Gather Documentation: Collect death certificates, asset records, and any wills or trusts if available. For example, revisit your will or trust to ensure that all beneficiaries are up to date. Consult a Knowledgeable Attorney.