When a person dies, the property in her revocable trust will automatically pass to the beneficiaries without the need for probate. The assets in a revocable trust will still be subject to estate taxes when a person dies. People often decide not to create revocable trusts because they can be complicated and time-consuming. There are basically no differences in the estate tax planning that can be accomplished through a will versus a revocable trust. Irrevocable trusts are similar to revocable trusts, except that you can never change them.
People typically create irrevocable trusts because they want to give away property.
The objective is to avoid having it included in their taxable estates when they die. Crummey trusts are a common type of irrevocable trust named after a Colorado taxpayer. Back in the 1960s, the Crummey case revolutionized the way many types of irrevocable trusts are written. The IRS does not like the Crummey trust, and from time to time it challenges taxpayers who use such trusts. Most of the time taxpayers win, so Crummey trusts remain a popular estate planning tool.