One of the defining features of an Irrevocable Trust is that it cannot be amended, either at it’s outset, or at the occurrence of a specified event, such as the death of the Grantor.
Sometimes an irrevocable trust contains the ability for it to be modified through the use of a power of appointment. A power of appointment is a specific power granted usually to a surviving spouse or a beneficiary that allows them to “appoint” income or principal of a trust or a share of a trust which benefits them, to or among one or more people who may be different than what the trust itself calls for.
Sometimes the powers of appointment limit who can be an eligible “appointee” of trust income or assets, such as only descendants of the Grantor, or a certain class of descendants.
While not technically an amendment power, the power of appointment is a way, if built into the original trust instrument, to permit changing the ultimate beneficiaries of an irrevocable trust.
Aside from that, the only way typically, that a revocable trust could be amended is through a process known as “reforming a trust”. The requires petitioning the court to allow a surviving spouse or one or more beneficiaries to modify the terms of the irrevocable trust. This is very difficult to do, but a judge may allow a trust to be reformed if the trust creates an undue burden on the surviving spouse or beneficiaries, or if the trust is determined to be unable to serve its original intent.