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 Missouri, an irrevocable trust is a type of trust that, once established, cannot be altered, amended, or terminated by the grantor without the consent of the trust's beneficiaries. The creation of an irrevocable trust involves a permanent transfer of ownership of assets from the grantor to the trust, effectively removing the assets from the grantor's taxable estate. This can result in significant tax advantages, such as reduced estate taxes, because the assets are no longer considered part of the grantor's property. Missouri law requires that the terms of the trust must clearly indicate the intention for the trust to be irrevocable for it to be treated as such. If the trust document does not specify, the trust may be considered revocable. It's important to note that while the grantor cannot unilaterally modify an irrevocable trust, under certain circumstances, modifications may be possible with the agreement of the beneficiaries or by court order if it is deemed to be in the best interest of the trust's purposes.