An irrevocable trust is a trust that cannot be amended, modified, or terminated by the grantor, settlor, or trustor (person who created the trust) after it is created—at least not without the permission of the beneficiary or beneficiaries.

Irrevocable trusts generally offer tax benefits that revocable trusts do not. This is primarily because the grantor, settlor, or trustor who creates an irrevocable trust permanently transfers (gifts) all right of ownership of the assets to the trust and its beneficiaries.

Laws vary from state to state but a trust is usually irrevocable unless the grantor, settlor, or trustor specifies otherwise in the trust agreement.

In Washington State, an irrevocable trust is a type of trust that, once established, typically cannot be changed, modified, or dissolved by the person who created it, known as the grantor, settlor, or trustor. The main characteristic of an irrevocable trust is that the grantor transfers ownership of assets to the trust, relinquishing control and any rights to amend the trust terms, which effectively removes the assets from the grantor's taxable estate. This can result in significant tax advantages, such as reduced estate taxes and protection from creditors, because the assets are no longer considered part of the grantor's property. While the laws governing trusts can differ across states, in Washington, the terms of the trust document will generally determine whether a trust is irrevocable or not. If the trust document does not explicitly state that the trust is revocable, it is presumed to be irrevocable. However, under certain circumstances and with the consent of all beneficiaries, modifications to an irrevocable trust may be possible through court proceedings or non-judicial reformations.