An investment partnership pays no federal income tax itself. Under Subchapter K of the Internal Revenue Code, the fund files an informational return and passes every item of income, gain, loss, deduction, and credit through to its partners, who report and pay tax on their share whether or not cash was distributed. The investment partnership tax rules that flow from this structure govern how the partnership allocates results, how partners track basis, when losses can be deducted, how carried interest is taxed, and what the partnership must file each year.
What Counts as an Investment Partnership
The label matters because the code treats an investment partnership differently from one running an active business. An investment partnership primarily holds stocks, securities, commodities, and similar assets for appreciation, interest, or dividend income rather than providing continuous services to customers. Gains from selling those assets generally receive capital gains treatment, even with frequent trading, as long as the fund trades for its own account.
Income should come predominantly from investment sources. If the partnership earns substantial fees from management services or other active work, the IRS may challenge investment-entity status, which changes how the income is classified and taxed.
Flow-Through Taxation and What the Partnership Files
The partnership is a conduit. It calculates results and passes them to partners, who pay tax on individual returns.1Internal Revenue Service. Partnerships This avoids the double tax that hits C corporations.
The partnership reports its results on Form 1065, an informational return.2Internal Revenue Service. Form 1065 – U.S. Return of Partnership Income The taxable year must match the majority partners’ year; most partnerships use a calendar year. A different fiscal year is allowed only with a legitimate business purpose.3Office of the Law Revision Counsel. 26 USC 706 – Taxable Years of Partner and Partnership
Certain items must be reported separately rather than folded into ordinary income, because they could affect individual partners differently. Capital gains, charitable contributions, tax-exempt income, and guaranteed payments each get their own line. Every item is then allocated to each partner and reported on Schedule K-1.4Internal Revenue Service. Schedule K-1 (Form 1065) – Partner’s Share of Income, Deductions, Credits, etc.
Partners owe tax on their share whether or not cash is distributed. A partner allocated $500,000 of long-term capital gain owes tax on it even if every dollar stays in the fund. For 2026, the top federal rate on long-term capital gains is 20%. Partners whose modified adjusted gross income exceeds $250,000 (married filing jointly) or $200,000 (single) also owe the 3.8% Net Investment Income Tax, pushing the effective top federal rate on investment gains to 23.8%.5Internal Revenue Service. Net Investment Income Tax
How Income and Losses Are Allocated Among Partners
How the partnership splits income and losses is not automatic. It follows the partnership agreement, but only if the allocations have what Section 704(b) calls substantial economic effect. Otherwise, the IRS reallocates based on the partners’ actual economic interests.6Office of the Law Revision Counsel. 26 USC 704 – Partner’s Distributive Share The standard requires that tax allocations track real economic outcomes: a partner allocated income actually receives economic benefit, and a partner allocated losses actually bears economic cost.
Built-In Gains on Contributed Property
When a partner contributes property whose fair market value differs from its tax basis, Section 704(c) requires special allocations to keep the built-in gain or loss with the contributing partner. If a partner contributes stock with a $1 million basis and a $3 million fair market value, the $2 million built-in gain must ultimately be allocated to the contributing partner when the partnership sells the stock, not spread across all partners.
Treasury Regulations require a reasonable method consistent with preventing tax shifting.7eCFR. 26 CFR 1.704-3 – Contributed Property If the contributed property is distributed to a different partner within seven years, the contributing partner may have to recognize the built-in gain as though the property were sold. Built-in losses can only reduce the contributing partner’s share of income.
How Partnership Debt Affects Partners
Partnership liabilities feed directly into each partner’s tax picture. An increase in a partner’s share of partnership debt is treated as a cash contribution, raising outside basis. A decrease is treated as a cash distribution, reducing it.8Internal Revenue Service. Recourse vs. Nonrecourse Liabilities This feature is unique to partnerships; S corporation shareholders and trust beneficiaries generally cannot include entity-level debt in basis.
Recourse liabilities are allocated to partners who would bear the economic loss if the partnership couldn’t pay. Nonrecourse liabilities, secured only by partnership property, spread more broadly under a different set of rules. For funds that borrow to fund positions, this allocation can materially change how much loss each partner can deduct.
Outside Basis: Why Partners Have to Track It
Every partner keeps a running outside basis in their partnership interest. That number governs two questions: how much loss the partner can deduct, and whether a distribution triggers taxable gain.9Office of the Law Revision Counsel. 26 USC 705 – Determination of Basis of Partner’s Interest
Outside basis goes up with cash and property contributions, allocations of taxable and tax-exempt income, and increases in the partner’s share of partnership liabilities (treated as a deemed cash contribution). It goes down with cash distributions and the adjusted basis of distributed property, allocations of losses and nondeductible expenses, and decreases in the partner’s share of liabilities (treated as a deemed cash distribution).
Outside basis can never fall below zero. Losses allocated in excess of basis are suspended and carried forward indefinitely, becoming deductible in a later year when the partner’s basis increases through additional income allocations or new contributions.10Internal Revenue Service. New Limits on Partners’ Shares of Partnership Losses Frequently Asked Questions
How Distributions Are Taxed
Cash distributions are generally not taxable. Partners have already paid tax on their share of partnership income as it was earned, so cash coming out is treated as a return of capital that reduces outside basis.11Office of the Law Revision Counsel. 26 USC 731 – Extent of Recognition of Gain or Loss on Distribution
Gain is recognized only when a cash distribution exceeds the partner’s adjusted outside basis, and it’s generally capital gain. Investment partnerships need to watch one wrinkle. Marketable securities count as cash for this rule. If the partnership distributes appreciated stock to a partner, the fair market value is treated like cash, and gain results if the value exceeds the partner’s basis.
Loss recognition on distributions is far more limited. A partner can recognize a loss only in a liquidating distribution, and only when the partner receives nothing other than cash, unrealized receivables, or inventory. Non-liquidating distributions never produce a deductible loss.
Four Loss Limitations Partners Hit in Order
Partners face up to four separate hurdles before deducting their share of losses. They apply in sequence, and clearing one does not clear the next.
- Basis limitation under Section 704(d): losses cannot exceed the partner’s outside basis at year-end. Excess losses carry forward indefinitely.10Internal Revenue Service. New Limits on Partners’ Shares of Partnership Losses Frequently Asked Questions
- At-risk limitation under Section 465: losses that survive the basis test are then capped at what the partner has at risk, generally cash contributions plus amounts borrowed for which the partner bears personal liability. Nonrecourse debt typically does not count, so the at-risk figure can run below outside basis.12Customs Mobile. 26 USC 465 – Deductions Limited to Amount at Risk
- Passive activity rules under Section 469: passive losses can only offset passive income. For most limited partners in investment partnerships, their share of losses is passive unless they materially participate.
- Excess business loss limitation under Section 461(l): for noncorporate taxpayers, business losses above an annually inflation-adjusted threshold are not deductible in the current year and roll forward as net operating losses.
The at-risk rules catch what the basis rules miss. A partner’s at-risk amount can go negative when distributions push it below zero. If a partner deducted losses against at-risk amounts and later takes a distribution that drives that balance negative, some of those prior deductions can be recaptured as income.
Carried Interest and Section 1061
Carried interest is the performance share fund managers receive, typically 20% of gains after limited partners get their preferred return. Because it’s allocated as a partnership profit share rather than paid as salary, it historically qualified for long-term capital gains rates. Section 1061 tightens that by requiring a three-year holding period at the partnership level.13Internal Revenue Service. Section 1061 Reporting Guidance FAQs
The rule applies to “applicable partnership interests” (APIs), meaning partnership interests received in connection with performing services for the fund. If the partnership sells an asset held for more than one year but three years or fewer, the gain that would otherwise be long-term capital gain is recharacterized as short-term for the API holder and taxed at ordinary rates up to 37%.14Office of the Law Revision Counsel. 26 USC 1061 – Partnership Interests Held in Connection with Performance of Services Only assets held more than three years generate long-term capital gain for the carried interest holder.
Several categories escape Section 1061 entirely. Qualified dividends and certain real property gains are not subject to the three-year recharacterization. The rule also does not apply to the manager’s share of profits attributable to their own invested capital; only the performance allocation is affected.
The Capital Interest Exception
Fund managers who invest their own capital alongside limited partners can claim a capital interest exception to shield returns on that invested capital from the three-year rule. To qualify, the partnership agreement must maintain a separate capital account for the manager’s invested capital, and allocations on it must follow a pattern reasonably similar to allocations made to unrelated limited partners who hold at least 5% of total capital contributions. Contemporaneous books and records must clearly identify which allocations relate to invested capital versus the API. Failing to keep this separation can pull the manager’s entire interest, including returns on invested capital, into Section 1061.
Holding period is measured at the partnership level based on when the partnership acquired the underlying asset. The partnership reports this on a supplemental statement attached to the K-1. Sloppy tracking creates real audit exposure, because the IRS can reclassify gains from long-term to short-term if the records don’t support the claimed holding periods.
Self-Employment Tax on Partner Income
Whether a partner’s share is subject to self-employment tax depends on the partner’s role. General partners typically owe self-employment tax on their distributive share of ordinary income. Limited partners are generally exempt: Section 1402(a)(13) excludes a limited partner’s distributive share from self-employment income, other than guaranteed payments for services actually rendered.15Office of the Law Revision Counsel. 26 USC 1402 – Definitions
What counts as a “limited partner” for this purpose has been heavily litigated. The Tax Court has applied a functional analysis, asking whether a partner actually behaves like a limited partner regardless of formal title. The Fifth Circuit rejected that approach in early 2026, holding that a limited partner in a limited partnership qualifies for the exclusion based on limited liability status alone. Until other circuits weigh in or the IRS issues final regulations, the exclusion’s scope remains uncertain for partners in LLCs taxed as partnerships, where every member has limited liability but some are deeply involved in management.
For fund managers, this intersects with carried interest. The management fee component, typically a guaranteed payment, is clearly subject to self-employment tax. Treatment of the carried interest allocation is less settled and depends on how the manager’s interest is structured.
UBTI for Tax-Exempt Partners
Pension funds, endowments, and other tax-exempt entities that invest in partnerships face a trap. Even though they are normally exempt from income tax, they can owe tax on unrelated business taxable income (UBTI) generated by the partnership, because the character of the income carries through.16Internal Revenue Service. UBIT: Special Rules for Partnerships
Pure investment income (dividends, interest, capital gains) generally does not create UBTI. The problem arises with leverage. Under Section 514, income from debt-financed property becomes partially taxable to tax-exempt partners in proportion to the debt used to acquire the property.17Internal Revenue Service. Unrelated Business Income from Debt-Financed Property Under IRC Section 514 If a partnership borrows to buy securities, the exempt partner’s share of income from those securities is UBTI to the extent of the leverage ratio.
That’s why many institutional investors care whether a fund uses margin or other borrowing. A fund trading entirely with contributed capital poses no UBTI risk for exempt partners. A leveraged fund can generate significant UBTI, forcing the exempt partner to file Form 990-T and pay tax at trust or corporate rates on the debt-financed portion. Managers often address this by creating parallel structures: a leveraged vehicle for taxable investors and an unleveraged one for tax-exempt ones.
Foreign Partners and Withholding
Foreign partners add substantial compliance. The partnership must withhold tax on a foreign partner’s share of effectively connected income at the highest applicable rate: 37% for noncorporate foreign partners and 21% for corporate foreign partners.18Internal Revenue Service. Who Must Withhold on Partnership Withholding The obligation is triggered by the allocation of income, not by any cash distribution.
For income not effectively connected with a U.S. trade or business, such as certain dividends and interest (FDAP income), a flat 30% withholding rate applies to the gross amount unless a tax treaty provides a lower rate. No deductions or netting are allowed against FDAP income.19Internal Revenue Service. Fixed, Determinable, Annual, or Periodical (FDAP) Income
Partnerships with any international activity, foreign partners, or foreign-source income must also file Schedules K-2 and K-3, which report detailed international tax information alongside Form 1065 and each K-1. A domestic filing exception exists for partnerships with no foreign partners and no foreign activity, but it requires specific partner notifications and no partner requesting a K-3.
Section 199A: Mostly Off the Table for Investment Income
The qualified business income deduction under Section 199A allows eligible taxpayers to deduct up to 20% of qualified business income from pass-through entities, and the One Big Beautiful Bill Act made this deduction permanent starting in 2026. But it specifically excludes investment-type income: capital gains, interest not allocable to a trade or business, dividends, and guaranteed payments are all carved out.20Internal Revenue Service. Qualified Business Income Deduction
For most investment partnerships, the deduction is largely irrelevant. The income these funds generate falls squarely into the excluded categories. Partners who see QBI-related items on a K-1 should verify they actually come from a qualifying trade or business activity within the partnership, not from the investment portfolio.
Filing Deadlines and Late Penalties
Form 1065 is due by the 15th day of the third month after the close of the tax year, which is March 15 for calendar-year partnerships.21Internal Revenue Service. Publication 509 (2026), Tax Calendars An automatic six-month extension pushes the deadline to September 15. The partnership must also furnish a K-1 to each partner by the same due date, including extensions. Partners rely on the K-1 to file their own returns, so a late K-1 cascades into missed individual deadlines.
The late-filing penalty is steep and scales with the number of partners. Under Section 6698, it’s calculated per partner, per month the return is late (including extensions), for up to 12 months. The base penalty is $195 per partner per month, adjusted annually for inflation.22Office of the Law Revision Counsel. 26 USC 6698 – Failure to File Partnership Return For a fund with 50 partners, even a one-month delay produces a penalty in the thousands. A full 12 months becomes eye-watering.
Investment partnerships operating across state lines face additional filings. Many states tax partnership income earned within their borders, and some require the partnership to withhold on behalf of nonresident partners or file composite returns covering all out-of-state partners. State filings multiply quickly for funds with diversified portfolios or partners spread across multiple states.
The Centralized Partnership Audit Regime
Since 2018, most partnerships have been subject to the centralized audit regime created by the Bipartisan Budget Act of 2015. The IRS audits and assesses tax adjustments at the partnership level rather than chasing individual partners.23Internal Revenue Service. BBA Centralized Partnership Audit Regime The partnership must designate a Partnership Representative with sole authority to bind the partnership and all partners during an audit.
When the IRS finds an underpayment, it calculates an “imputed underpayment” at the partnership level. The partnership can pay it directly or elect to push the adjustments out to the individual partners for the reviewed year. Paying at the partnership level is simpler but uses the highest individual tax rate. Pushing out shifts the tax to partners who were there when the income was earned, but it requires cooperation from former partners who may have left the fund.
Partnerships with 100 or fewer partners can elect out of the centralized regime entirely, but only if every partner is an eligible type: individuals, C corporations, S corporations, foreign entities that would be C corporations if domestic, and estates of deceased partners. Partnerships, trusts, and disregarded entities as partners disqualify the fund from electing out. For S corporation partners, all shareholders count toward the 100-partner limit. The election must be made annually on a timely filed Form 1065.24Internal Revenue Service. Elect Out of the Centralized Partnership Audit Regime Most large investment funds won’t qualify, which makes the Partnership Representative appointment a critical piece of the fund’s organizational documents.