A person who makes a will (a testator) may update or revise the will at any time during their lifetime if the testator has the required mental capacity (is of sound mind) and the document is executed or signed with the required formalities (such as witnesses and signatures), as provided by the state’s laws.

There are generally two ways to update a will—execute a new will (usually the best option) with the required witnesses, signatures, and other formalities—or execute a codicil (a supplement to an earlier will), with the required witnesses, signatures, and other formalities, as provided by the state’s laws.

Laws regarding the use of codicils and the required formalities for wills and codicils vary from state to state and are usually located in a state’s statutes—often in the estates code or probate code.

A testator who updates their will by executing a new will should usually destroy the previous will to avoid questions regarding which will reflects the testator’s true intent and to avoid competing wills being offered for probate (recognition by the court).

In Iowa, a testator has the right to update or revise their will at any time as long as they have the mental capacity to do so and adhere to the necessary legal formalities. These formalities include having the will properly witnessed and signed in accordance with Iowa's laws. To update a will, the testator can either create a new will or add a codicil to the existing will. A codicil is a document that amends, rather than replaces, a previously executed will and must also be executed with the same formalities as a new will. When a new will is made, it is advisable for the testator to destroy any previous versions to prevent confusion and ensure that the most recent will is recognized as the true expression of their wishes. The specific requirements for wills and codicils in Iowa can be found in the state's probate code.