Trust under will is a legal arrangement wherein a person's assets are transferred to a trustee to be held for the benefit of a beneficiary. Synonyms for this term are testamentary trust, will trust, and trust created by a will. Testamentary trust is the most commonly used synonym, and it is often included in estate planning documents. A will trust is another term used to refer to this legal arrangement, as it is established by the provisions of a will. The main purpose of trust under will is to ensure that a person's assets are managed and distributed according to their wishes after their death.