An Intentionally Defective Grantor Trust (IDGT) is a unique estate-planning tool that allows you to separate and isolate... moreAn Intentionally Defective Grantor Trust (IDGT) is a unique estate-planning tool that allows you to separate and isolate certain trust assets. It's a way to split assets, separating income tax from estate tax. Many people go to a trusts lawyer to find ways to reduce taxable estate after their death.