The word for a share in a master limited partnership is a unit, and the person holding it is a partner rather than a shareholder. The vocabulary tracks a real difference in structure.
A limited partner gets a Schedule K-1 every year instead of the tax form most dividend investors are used to, and that same structure is why these holdings sit badly inside an IRA.
Units, Unitholders, and the General Partner's Unlimited Liability
An MLP is one business wearing two hats: a publicly traded entity and a limited partnership. It has one or more general partners who run day-to-day operations, and limited partners, the outside investors, who hold an interest but no role in operations.
If you buy in, you're a limited partner, and your ownership is measured in units. That makes you a unitholder. Your liability is capped at what you put in: you can't lose more than you invested.
The general partner side looks different. A general partner typically holds a stake of at least 2%, and can increase it. That partner gets first priority on cash distributions, and carries unlimited liability in exchange.
The 90% Income Test and Why Energy Dominates the Category
The first MLP appeared in 1981, and the structure caught on gradually because of its tax treatment. Then the Tax Reform Act of 1986 narrowed the field: to use the MLP structure, a business needs at least 90% of its income coming from natural resources, commodities, or real estate.
Real estate qualifies under that test, but the REIT structure claimed most of that business, leaving only a scattering of commercial real estate MLPs. What fills the category today is energy, and oil and gas in particular. Within that sector, MLPs tend to sort by where they sit on the supply chain:
- Pipeline MLPs
- Gathering and processing MLPs
- Exploration and production MLPs
- Specialty MLPs
How closely a given MLP's fortunes track the price of oil or gas matters. The more dependent it is on commodity prices, the more volatile it can be.
Buying Units Through a Brokerage, a Fund, or an ETF
Because MLPs are publicly traded, the buying mechanics are familiar. You place a trade through your online brokerage account, and you can sell units on the exchanges much as you'd sell stock. The vocabulary changes; the process doesn't.
There's also a bundled route. MLP mutual funds and ETFs hold multiple MLPs in a single investment, which spreads exposure across several partnerships rather than concentrating it in one. Fund structures differ in how they report to their investors, and a fund's own documents spell that out.
Some investors go through a brokerage firm with specific experience in MLPs, on the theory that someone who reviews these financials regularly can read the metrics faster.
The Filings on EDGAR: Prospectus, 10-K, and 10-Q
Every public company files financial statements with the U.S. Securities and Exchange Commission, and MLPs are no exception. Those filings are searchable through the SEC's EDGAR system, free to anyone:
- Form 424, the prospectus
- Form 10-K, the annual report
- Form 10-Q, quarterly reports
Read them and you can see how the partnership makes money, what it owes, and how much of its cash flow it's sending out the door. A financial advisor can help work through a specific MLP's numbers if the filings run dense, which they often do.
Pass-Through Taxation Removes the Corporate Tax Layer
As long as the 90% income test is met, an MLP gets pass-through treatment: it doesn't pay taxes the way a corporation does. The tax burden passes down to the investors instead.
Limited partners receive quarterly distributions, sometimes called MLP checks. Because profits aren't reduced by corporate tax first, those distributions may be larger than what a comparable taxpaying corporation could pass along.
Compare that with a C corporation, which pays corporate tax before any profit reaches shareholders.
Distributions Are Taxed as Income or Deferred Until You Sell
Cash distributions to limited partners fall into one of two buckets, and the difference changes when you pay tax.
| Classification | When it's taxed | What tax applies |
|---|---|---|
| Income | In the year received | Federal and state income tax |
| Return of capital | When you sell the units | Capital gains tax on any profit |
The return-of-capital piece is where the appeal lies for long-term holders. Long-term capital gains rates are typically lower than income tax rates, so tax that's deferred can also end up assessed at a lower rate.
Picture a unitholder who holds the same MLP for years. Distributions arrive quarterly, and the portion classified as return of capital isn't taxed as it lands. The reckoning comes at the sale, when profit on the units is subject to capital gains tax.
What Arrives on the Schedule K-1, and When
Each year, limited partners receive a Schedule K-1 from the MLP showing their share of the partnership's income, deductions, credits, gains, and losses. That information goes onto your annual tax return, and the MLP files a copy of the K-1 with the IRS.
This is the part investors most often underestimate. A K-1 is a partnership form, not a dividend statement, and MLP investors commonly hire a CPA or another tax professional to handle the return.
Worth knowing too: partnership forms have a reputation for arriving later in tax season than the forms most investors get from brokerages, and a corrected K-1 can show up after the original. Filers who like to be done in February sometimes find themselves waiting, or amending.
UBTI and Retirement Accounts
MLPs generate unrelated business taxable income, or UBTI. A pension, 401(k), IRA, or other tax-exempt fund doesn't shelter that kind of income cleanly, which makes MLPs a problematic holding inside one. In practice, they often aren't available in those accounts anyway.
Slow Growth, Volatility, Complexity, and Sector Concentration
Growth is the first limit. The businesses at the center of the category, oil exploration and pipeline construction, aren't fast movers, and the payout model works against expansion: most of the income goes out to investors, so the partnership keeps little cash to put back into itself.
Price swings are the second. MLPs have historically moved more than traditional stocks and bonds. Past performance doesn't dictate future results, but the volatility is part of the asset's character.
Then there's the structure, which is intricate on both the liability and the tax side. Pass-through treatment works in an investor's favor and, at the same time, is one of the reasons an MLP is harder to evaluate than a plain share of stock.
The sector question sits on top of all of it: with so much of the category in energy, one piece of legislation or one regulatory shift aimed at oil and gas can touch a large share of it at once.
How MLPs Compare With Sole Proprietorships, LLCs, and Corporations
Pass-through taxation isn't unique to MLPs; sole proprietorships and LLCs are taxed that way too. Neither is the limited liability a unitholder gets, which puts a limited partner in roughly the position of an LLC owner or an individual shareholder in a corporation.
What has no counterpart in those setups is the general partner, whose liability isn't capped at all.
For an outside investor, that asymmetry is mostly a governance fact rather than a personal risk, since your exposure stays capped at your investment. It does explain why the general partner's distribution priority is written into the deal.
Where MLPs Usually Fit: Taxable Accounts and Long Holds
The profile that comes up most often has three parts:
- Investors seeking long-term passive income, since distributions arrive quarterly and not all of them are taxed as income when received.
- Investors already working with tax or financial professionals, given the K-1 and the structure behind it.
- Investors buying in a taxable account rather than a retirement account, because of UBTI.
Cash Flow on One Side, Complexity and Sector Risk on the Other
The draw of an MLP is cash flow that hasn't been taxed at the company level, with part of it deferred until you sell. The cost shows up as a more complicated return, a slower-growing set of industries, and concentration in a sector where one regulatory change can move a lot of holdings at once.
Which account the units would sit in, and who handles the K-1 when it shows up in spring, are the sort of details that get settled before a purchase rather than after it.
