Trusts come in many shapes and sizes, but you could divide them into two broad groups—grantor trusts and non-grantor trusts. There's also a third type, however—the "intentionally defective grantor trust," or IDGT, that is designed to break tax rules for estate planning purposes.

With a grantor trust, the grantor—the person who creates it—retains considerable power over how it's administered, including the rights to amend, revoke, or terminate the trust. The grantor also maintains control over the trust assets. Typically, the grantor is a beneficiary of the trust income and principal. For instance, the grantor could be the primary beneficiary, with other family members entitled to the remainder. The grantor also can act as the trustee responsible for administering the trust.

With non-grantor trusts, however, grantors give up all of those rights. They aren't entitled to the income or the principal and, usually, payouts from the trust go to other family members. Also, the grantor cannot be the trustee of a non-grantor trust.

Now consider the tax implications. Because grantors retain control over grantor trusts, they're taxed for the income the trusts produce. For grantors in higher tax brackets—including the top bracket, with its 39.6% tax rate—the income tax consequences can be significant. In contrast, income earned by a non-grantor trust is taxed to the trust itself, not to the grantor.

But that can be a problem because trusts pay comparatively high tax rates. For instance, that top 39.6% rate kicks in when trust income exceeds $12,500 in 2017. Compare that to the $470,700 threshold for the top rate for a married grantor who files a joint return, or $418,400 for a single filer. That can translate into very high taxes for a non-grantor trust.

But that's where an IDGT may come to the rescue. As long as the grantor retains certain powers, the grantor, rather than the trust, will be taxed on trust income—even if none of that income goes to that person. An IDGT trust is set up so that it will purposely fail to qualify as a non-grantor trust, thus avoiding the higher taxes that come with the non-grantor designation.

What about estate and gift taxes? Money you transfer to an IDGT is treated as a taxable gift, but there's a current individual exemption of $5.49 million in 2017 that could reduce or eliminate your tax liability for the gift. (There also are other ways to structure this transfer so that it's not considered a gift at all.) In addition, the assets you transfer into the trust are no longer in your taxable estate, whose value will be reduced further by the annual taxes you pay on trust assets.

But IDGTs are complex arrangements, and you'll need the help of an experienced estate planning professional to create a trust that fits your needs. Seek expert assistance.