Oral Trusts Are Legal but Hard to Prove
Most people associate trusts with formal, signed documents. Arizona law takes a broader view. A trust does not have to be in writing to be valid. But proving an oral trust exists is a much higher bar than proving the terms of a written one.
Except as required by a statute other than this chapter, a trust need not be evidenced by a trust instrument, but the creation of an oral trust shall be established only by clear and convincing evidence and the terms of the oral trust shall be established by a preponderance of the evidence.
A.R.S. § 14-10407Clear and convincing evidence is a demanding standard. It means the evidence must be highly and substantially probable, not just more likely than not. Anyone claiming an oral trust exists would need testimony, documentation, or other proof strong enough to leave little room for doubt about the settlor's intentions.
Written Trusts Require Written Changes
The second half of this statute draws an important line. Once a trust is created in writing, it can only be amended or revoked through a written instrument executed by the settlor. You cannot modify a written trust with a verbal instruction, a phone call, or a casual conversation.
This rule protects settlors and beneficiaries alike. It prevents disputes over whether someone verbally changed the terms of a trust before passing away or becoming incapacitated. It also means that anyone who claims a written trust was "really" supposed to say something different would need to go through the formal amendment process rather than relying on secondhand accounts of what the settlor said.
For practical purposes, this is one of the strongest reasons to put a trust in writing from the start. A written trust instrument is clear, verifiable, and far more difficult to dispute than an oral arrangement that may come down to one person's word against another's.
