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 New Hampshire, an irrevocable trust is a type of trust that, once established, typically cannot be changed, modified, or terminated by the person who created it, known as the grantor, settlor, or trustor, without the consent of the trust's beneficiaries. The main characteristic of an irrevocable trust is the transfer of ownership of assets from the grantor to the trust, which is managed for the benefit of the beneficiaries. This transfer is considered permanent, and it often results in tax advantages because the assets are no longer considered part of the grantor's estate for tax purposes. New Hampshire trust laws are codified in the New Hampshire Revised Statutes Annotated (RSA), and specific provisions regarding the modification or termination of irrevocable trusts can be found there. It's important to note that while the general rule is that irrevocable trusts cannot be altered, there may be exceptions under certain circumstances as provided by state law or the terms of the trust itself.