A codicil is the document used to implement changes to your will if a completely new will is not needed to make the desired change or changes. To be legally effective, a codicil must be executed with the same degree of formality as the will itself. You cannot change your will by merely writing something in or on the original will, and it is a very big mistake to write in changes on a will in such a manner. For this reason, we strongly recommend that you seek legal assistance from a licensed attorney if you desire to change your will.