I posted the following to a discussion board for an estate planning magazine, the editors liked it, so I’m reposting here.
Master Limited Partnerships (MLPs) are excellent tools for estate planning:

1. MLP distributions (around 8% yield right now) are considered return of capital, meaning that distributions reduce your basis in the MLP, while allocated net income increases your basis.
2. Tax Shield: Because MLPs own large hard assets (like pipelines) with high depreciation (non-cash) expenses, allocated income to an investor is usually less than 20% of cash distributions in a given year for the first several years of ownership. This creates a tax deferral, which is recaptured when you sell the MLP.
3. When you sell an MLP: (a) the gains from your purchase price to selling price are taxed at capital gains rates, and (b) the difference between your purchase price and your basis (which has been reduced over time) is taxed at ordinary income rates.
4. But, if you die while holding an MLP, the tax deferrals you have accumulated over time are washed away along with the capital gains taxes, and whoever receives those MLPs after you die has a new stepped up basis, so those tax deferrals are not recouped by or due to the IRS.

So in addition to being great income vehicles with healthy tax shields, MLPs benefit from a stepped up basis when you die that allows you to memorialize the tax deferrals you made through the years.