When your MLP cost basis reaches zero — from years of return-of-capital distributions exceeding income allocations — every distribution after that becomes immediately taxable as capital gain under IRC §731(a). Your tax-deferred ride is over. But reaching zero basis doesn't mean you should sell.
By Lucas Andersen — Last updated April 9, 2026
Your outside basis starts at your purchase price plus your initial share of partnership liabilities (Item K). Each year, K-1 adjustments reduce it: cash distributions (Box 19A) under IRC §733, ordinary losses (Box 1), and liability decreases (Item K) all erode basis. Income allocations and liability increases add basis back, but for most MLPs the net annual effect is negative by 3–6% of original cost. Pipeline MLPs (EPD, ET, MPLX, WES, PAA) typically reach zero in 7–15 years depending on purchase price and distribution growth. Royalty MLPs (NRP, BSM) reach zero in 3–5 years due to depletion mechanics. For the full erosion mechanics, see how MLP distributions erode your basis.
IRC §731(a)(1) states: “In the case of a distribution by a partnership to a partner — gain shall not be recognized to such partner, except to the extent that any money distributed exceeds the adjusted basis of such partner’s interest in the partnership.” Once your adjusted basis equals zero, every dollar of cash distribution exceeds basis, and every dollar is recognized as gain. This gain is characterized as capital gain — long-term if you have held for more than one year — taxed at 0%, 15%, or 20% depending on your income bracket. It is NOT ordinary income. Basis cannot go below zero; the excess triggers gain recognition instead.
The table below quantifies the ongoing annual cost of holding an EPD position at zero basis, receiving $1,050/year in distributions ($2.10/unit × 500 units), at each LTCG rate bracket. The “phantom income” row shows additional tax when Box 1 is positive (+$200 illustrative).
| Tax Item | 0% LTCG | 15% LTCG | 20% LTCG |
|---|---|---|---|
| §731 gain on $1,050 distributions | $0 | $158 | $210 |
| 3.8% NIIT (if applicable) | $0 | $0 | $40 |
| Phantom income tax (Box 1 = +$200, at marginal rate) | $20 | $44 | $74 |
| Annual tax cost | $20 | $202 | $324 |
| After-tax yield (EPD at $30/unit, $15,000 FMV) | 6.9% | 5.7% | 4.8% |
| Cumulative tax cost over 5 years | $100 | $1,010 | $1,620 |
Phantom income row assumes Box 1 = +$200 in a strong year, taxed at 10%/22%/37% marginal rates respectively. In loss years, Box 1 is negative and the phantom income row is $0. NIIT applies to filers with MAGI above $200K single / $250K MFJ.
At zero basis, positive Box 1 income creates “phantom income” — you owe tax on allocated partnership income with no corresponding cash distribution earmarked for that tax. The cash you receive (Box 19A) is already fully taxed as §731 gain. The Box 1 income is additional taxable income on top of that, taxed at your ordinary marginal rate (up to 37%). CQP and fuel distribution MLPs (SUN, CAPL) are most at risk because their Box 1 is more frequently positive and larger than pipeline MLPs. In a strong commodity year, a zero-basis SUN holder might owe tax on both $1,050 of §731 gain AND $500+ of Box 1 phantom income — a combined tax bill that consumes 30–40% of the cash distribution.
Purchasing additional units creates new tax lots with fresh cost basis. Your zero-basis lots remain at zero — FIFO/specific identification rules apply to each lot independently. The new lots restore the deferral benefit: distributions allocated to new lots reduce their basis instead of triggering §731 gain. Example: you hold 500 zero-basis EPD units and buy 200 more at $30 ($6,000 basis). The 200 new units will absorb approximately $420/year in distributions ($2.10 × 200) against their $6,000 basis, deferring tax on those units for roughly 8–10 years. The 500 original units remain at zero and continue generating §731 gain on their $1,050 in annual distributions. Net effect: your blended after-tax yield improves because 29% of your distribution stream regains deferral.
At 15% LTCG, the after-tax yield on a zero-basis EPD position at $30/unit is approximately 5.7% (see table above). Compare this to alternatives: a CD at 4.5% (fully taxable at ordinary rates = ~3.0% after tax at 33%), a dividend stock yielding 3% (qualified dividend rate), or a bond fund at 5% (~3.3% after tax). Even after losing tax deferral, the zero-basis MLP often delivers a competitive after-tax yield. The question is whether that yield justifies the continued complexity of K-1 filing, basis tracking, and state tax exposure.
Selling a zero-basis position triggers the full gain: sale proceeds minus $0 basis = 100% gain. A portion is recharacterized as §751 ordinary income (taxed up to 37%), and the remainder is long-term capital gain (15–20%). The upside: under §469(g), selling your entire position releases all suspended passive losses accumulated during the hold. These released losses first offset the §751 ordinary income — saving tax at your highest marginal rate. For a long-held position with $2,000+ in suspended losses, this offset can reduce the sale-year tax bill by $500–$1,000+.
Under IRC §1014, heirs receive a stepped-up basis to fair market value on the date of death. If your basis is $0 and units are worth $15,000, the heir’s basis resets to $15,000. All §731 gain exposure: gone. All §751 recapture: gone. All embedded capital gain: gone. The heir starts a fresh deferral cycle. Suspended passive losses do expire unused under §469(g)(2) — they do not transfer to heirs. But the step-up is worth far more than the lost suspended losses would have saved. This is the mathematical basis for the “hold forever” MLP strategy.
Donating zero-basis MLP units to a qualified charity generates a charitable deduction equal to fair market value — with no capital gain or §751 ordinary income recognized. A $15,000 FMV donation of zero-basis units creates a $15,000 deduction (subject to AGI limitations) and zero tax on the $15,000 of embedded gain. This is more tax-efficient than selling, paying tax, and donating cash. Caution: the charity receives a K-1 and may not want the complexity. Donor-advised funds and university endowments are typically equipped to handle MLP K-1s; smaller charities may not be.
Reaching zero basis does not eliminate the §199A QBI deduction. If your K-1 reports qualified business income (Box 20 Code Z) and you are below the income threshold, you still receive the 20% deduction on that QBI — even at zero basis. This partially offsets the phantom income tax on positive Box 1 years.