Subchapter K is the part of the Internal Revenue Code, Sections 701 through 777, that sets the federal tax rules for partnerships and their partners. Its defining feature is pass-through taxation: the partnership itself pays no income tax, and profits, losses, deductions, and credits flow through to each partner’s personal return. The same framework governs most multi-member LLCs and joint ventures, not just entities that call themselves partnerships.
Which Businesses Subchapter K Covers
Section 761 defines a partnership broadly. It reaches any unincorporated group carrying on a business or financial venture together, whether or not the participants have a written agreement.1Office of the Law Revision Counsel. 26 U.S. Code 761 – Terms Defined Joint ventures, syndicates, and investment pools all fall inside the definition if two or more people share profits from a common activity.
Multi-member LLCs default to partnership taxation under the check-the-box regulations unless they file Form 8832 electing to be taxed as a corporation.2eCFR. 26 CFR 301.7701-3 – Classification of Certain Business Entities Single-member LLCs sit outside Subchapter K entirely. The IRS disregards them and treats their activity as belonging to the owner directly, reported on Schedule C or Schedule E rather than on a partnership return.
Publicly traded partnerships are another exception. A partnership whose interests trade on a securities exchange or a secondary market is generally reclassified as a corporation and loses pass-through treatment. It can keep partnership status only if at least 90 percent of its gross income each year comes from qualifying sources such as interest, dividends, real property rents, and income from natural resource activities like oil and gas exploration, mining, and pipeline transportation.3Office of the Law Revision Counsel. 26 USC 7704 – Certain Publicly Traded Partnerships Treated as Corporations That exception is why most energy-sector master limited partnerships are structured around qualifying income.
How Partnerships File and How Partners Get Taxed
Section 701 states the rule plainly: only the partners, not the partnership, are subject to income tax.4Office of the Law Revision Counsel. 26 USC 701 – Partners, Not Partnership, Subject to Tax This is the core difference from a Subchapter C corporation, where the company owes tax on its earnings and shareholders owe tax again when they receive dividends.
The partnership still files a return. Form 1065 is an informational return that reports the partnership’s income, deductions, and credits for the year. Each partner then receives a Schedule K-1 showing their individual share of every tax item, and those figures get carried to the partner’s Form 1040 where the tax is actually calculated.5Internal Revenue Service. Instructions for Form 1065
One consequence surprises new partners. You owe tax on your share of partnership income even if the business kept the cash and distributed nothing. If the partnership earned $200,000 and your share is 25 percent, $50,000 lands on your personal return whether or not you received a check.
Calendar-year partnerships must file Form 1065 by March 15. Form 7004 buys an automatic six-month extension to September 15. A fiscal-year partnership files on the 15th day of the third month after year-end.
Missing the deadline gets expensive fast. For returns due after December 31, 2025, the failure-to-file penalty is $255 per partner for each month or partial month the return is late, capped at 12 months.6Internal Revenue Service. Failure to File Penalty A five-partner partnership four months late owes $5,100 in penalties, even if the partnership itself has no tax liability, because Form 1065 is a compliance obligation separate from any tax due.
How Income and Losses Are Divided Among Partners
Section 704 lets partners split profits, losses, and other tax items however their partnership agreement provides. One partner can receive 60 percent of the profits while another receives 40, even if they contributed equal capital, as long as the arrangement is documented.7Office of the Law Revision Counsel. 26 U.S. Code 704 – Partner’s Distributive Share This is one of the biggest structural advantages of partnership taxation over the corporate form.
The flexibility comes with a limit. The IRS respects an allocation only if it has “substantial economic effect” under Treasury Regulation 1.704-1(b)(2). In practical terms, tax allocations have to track how partners actually share the economic ups and downs of the business.8eCFR. 26 CFR 1.704-1 – Partner’s Distributive Share Assigning all the losses to a high-income partner to shelter outside income, while other partners bear no real financial risk from those losses, does not survive scrutiny.
To fall within the safe harbor, a partnership agreement generally has to do three things: maintain capital accounts under the regulatory rules, liquidate by distributing remaining assets in proportion to positive capital account balances, and require any partner with a negative capital account at liquidation to restore that deficit. If an allocation fails the test, the IRS can override the agreement and reallocate items to reflect the partners’ actual economic interests in the business.
A Partner’s Basis in the Partnership
Every partner tracks an “outside basis,” a running balance in the partnership interest itself. Section 705 sets the mechanics. Basis goes up when the partner contributes cash or property, when income is allocated to them, and when they take on a larger share of partnership liabilities. Basis goes down for distributions, allocated losses, and decreases in the partner’s share of liabilities.9Office of the Law Revision Counsel. 26 U.S. Code 705 – Determination of Basis of Partner’s Interest
Basis controls two things partners care about. First, it decides whether a cash distribution triggers gain. If the partnership hands you $80,000 and your basis is $100,000, nothing is taxable. If your basis is $60,000, you recognize $20,000 of gain. Second, Section 704(d) caps loss deductions at your year-end basis. Losses beyond that cap carry forward and become deductible when your basis is high enough to absorb them.7Office of the Law Revision Counsel. 26 U.S. Code 704 – Partner’s Distributive Share
The regulation under Section 705 technically requires a partner to determine adjusted basis only when it matters for computing someone’s tax.10eCFR. 26 CFR 1.705-1 – Determination of Basis of Partner’s Interest Waiting is a bad idea. Reconstructing years of basis when you sell or the partnership dissolves invites errors, and partnerships are now required to report each partner’s capital account on Schedule K-1 using the tax basis method.
Contributions, Distributions, and Hot Assets
Getting property into a partnership is generally tax-free. Under Section 721, contributing property in exchange for a partnership interest produces no gain or loss for either the partner or the partnership.11Office of the Law Revision Counsel. 26 U.S. Code 721 – Nonrecognition of Gain or Loss on Contribution Any built-in gain is deferred rather than eliminated. The partnership takes the contributor’s adjusted basis in the property, and the gain surfaces later when the partnership sells the asset or distributes it to a different partner.
Distributions follow a similarly favorable default. Under Section 731, a partner recognizes gain only if the cash distributed exceeds the partner’s adjusted basis. Property distributions other than cash generally produce no gain; the partner absorbs the property and reduces basis.12Office of the Law Revision Counsel. 26 U.S. Code 731 – Extent of Recognition of Gain or Loss on Distribution A liquidating distribution that ends the partner’s entire interest triggers a final basis adjustment and can produce gain or loss depending on what is distributed.
The capital gain treatment has a major exception for what Subchapter K calls “hot assets.” Section 751 recharacterizes gain as ordinary income when the partnership holds unrealized receivables (including accounts receivable of a cash-basis business and various depreciation recapture amounts) or inventory that has appreciated substantially.13Office of the Law Revision Counsel. 26 U.S. Code 751 – Unrealized Receivables and Inventory Items The point is to stop partners from converting ordinary business income into lower-taxed capital gain through the structure of a distribution or sale. When a partner effectively trades their share of hot assets for cash or other property, that piece of the transaction is treated as a taxable sale between the partner and the partnership.
Selling a Partnership Interest
Section 741 sets the general rule for a sale: gain or loss on the sale of a partnership interest is treated as gain or loss from a capital asset.14Office of the Law Revision Counsel. 26 USC 741 – Recognition and Character of Gain or Loss on Sale or Exchange The gain equals the difference between the sale price and the seller’s adjusted basis in the interest, and it qualifies for long-term capital gain rates if the interest was held more than a year.
Section 751 overrides that treatment for the portion of the price attributable to the partnership’s hot assets. The seller has to allocate proceeds between hot assets and everything else, and the hot-asset portion is taxed as ordinary income.13Office of the Law Revision Counsel. 26 U.S. Code 751 – Unrealized Receivables and Inventory Items Selling a partnership interest is never as clean as selling stock. The character of the underlying assets reaches through the sale and shapes the tax bill.
Self-Employment Tax, Passive Losses, and the NIIT
Pass-through status avoids entity-level income tax, not payroll-type taxes. A general partner owes self-employment tax at 15.3 percent on their distributive share of the partnership’s trade or business income. The 12.4 percent Social Security portion applies up to the annually adjusted wage base; the 2.9 percent Medicare portion has no cap. High earners owe an additional 0.9 percent Medicare surtax above $200,000 (single) or $250,000 (married filing jointly).
Limited partners get a partial exception. Section 1402(a)(13) excludes a limited partner’s distributive share from self-employment tax, though guaranteed payments for services still count.15Office of the Law Revision Counsel. 26 USC 1402 – Definitions The scope of that exception is contested, and the law is not settled uniformly across circuits.
Section 469 adds a second gate. Even after clearing the basis limit, a partner’s losses may be classified as passive activity losses, deductible only against passive activity income rather than wages, portfolio income, or active business income.16Office of the Law Revision Counsel. 26 USC 469 – Passive Activity Losses and Credits Limited A partnership interest is treated as passive unless the partner materially participates, which generally means spending more than 500 hours a year in the activity.17Internal Revenue Service. Passive Activity and At-Risk Rules Limited partners face a stricter presumption of passivity and can meet the material participation tests only in narrow circumstances set by regulation. Disallowed passive losses carry forward and become fully deductible when the partner disposes of the entire interest in the activity.
Passive partnership income can also trigger the 3.8 percent net investment income tax under Section 1411 for partners with modified adjusted gross income above $200,000 (single) or $250,000 (married filing jointly). Those thresholds are not indexed for inflation. Income from a trade or business in which the partner materially participates is generally exempt from the surtax.
Partnership Audits Under the BBA
Since 2018, most partnerships have been audited under the centralized regime enacted by the Bipartisan Budget Act. The IRS examines the partnership as a single entity and assesses any resulting tax adjustment, called an “imputed underpayment,” at the partnership level rather than pursuing each partner separately.18Internal Revenue Service. BBA Centralized Partnership Audit Regime The partnership pays at the highest individual rate, and current-year partners bear the cost even when the audit covers a year with different partners.
Every partnership subject to the regime must designate a “partnership representative” with sole authority to act for the partnership in an audit. This role differs from the old “tax matters partner.” The representative does not have to be a partner, and their decisions bind everyone.
Partnerships have two ways to shift the assessment. They can elect to “push out” adjustments to the individuals who were partners in the reviewed year, who then report and pay on their own returns. Alternatively, small partnerships with 100 or fewer partners can elect out of the centralized regime entirely, provided every partner is an eligible type: an individual, a C corporation, an S corporation, or the estate of a deceased partner.19Internal Revenue Service. Elect Out of the Centralized Partnership Audit Regime A partnership with other partnerships, trusts, or disregarded entities as partners cannot elect out. The election has to be made on a timely filed return each year.