Some people choose to establish a testamentary trust as part of their estate plan. When you make this type of trust you get to determine its terms and direct how the trust will operate by writing your choices down in your last will and testament. Modifying the terms of your testamentary trust is very easy to do, though it will require you to meet the same standards that you met when you created your last will and testament.
You can often change the terms of the testamentary trust by drafting what is known as a codicil. A codicil is an amendment or alteration that applies to your last will and testament. Just like writing a will, your codicil must meet the legal requirements your state imposes. This requires, for example, printing the document, signing it, and having it signed by two witnesses.
In some situations you may want to make a drastic change to your testamentary trust that will also affect other parts of your will. In this situation, you may want to rewrite the will entirely. As long as you meet the same requirements that you did when you first created the will, you can change any terms you like. This holds true for the terms of the testamentary trust provisions you included in the will. As long as you meet state requirements, you can change those terms as you see fit.