In a second marriage, the estate planning goals are often contradictory: you want to ensure your new spouse has enough money to live comfortably if you die first, but you absolutely want your remaining wealth to go to your own children, not your spouse's children or their next husband/wife.
How the QTIP Solves the Problem
A Qualified Terminable Interest Property (QTIP) trust splits the difference. When you die, your assets go into the trust. Your surviving spouse receives all the income generated by the trust for the rest of their life. They are financially secure.
Best Practice
The Ironclad Guarantee
The surviving spouse cannot touch the principal (without the trustee's permission) and cannot change the final beneficiaries. When they die, the remaining principal goes exactly where you dictated—to your children.
The Marital Deduction Benefit
Despite the fact that your spouse doesn't actually own the assets in the QTIP, the IRS allows the transfer to qualify for the unlimited marital deduction. This defers all estate taxes until the second spouse dies.