Partnership Tax Rules: Form 1065, K-1 Allocations & Self-Employment Tax

A partnership is the default federal classification for any unincorporated business with two or more owners, including most multi-member LLCs. Its defining features are full pass-through taxation, flexible profit allocations governed by the partnership agreement, and a sharp distinction between general and limited partners that determines who pays self-employment tax. Layered on top is the modern centralized audit regime that fundamentally changed how the IRS assesses partnership adjustments.

Pass-Through Structure and Form 1065

The partnership is a reporting entity, not a taxpaying one. It files Form 1065 to report total income, deductions, and credits, then allocates each partner’s share on Schedule K-1. Partners carry those figures to their own returns — individuals report on Schedule E of Form 1040 — and pay tax at their personal rates whether or not cash was actually distributed.

Form 1065 is due on the fifteenth day of the third month after year-end, which is March 15 for calendar-year partnerships. This is a full month earlier than the individual deadline precisely so partners receive their K-1s in time to file. Form 7004 extends the partnership return to September 15.

Partner Type Tax-Treatment Matrix

Self-employment tax exposure depends on partner type and payment category, summarized below.

General vs Limited Partners and Self-Employment Tax

The partner classification drives self-employment tax. A general partner is treated as actively engaged in the trade or business, so their entire distributive share of ordinary income is subject to the 15.3 percent self-employment tax on Schedule SE. A limited partner, by contrast, is generally a passive investor whose distributive share is excluded from self-employment tax under IRC §1402(a)(13).

Guaranteed payments — fixed amounts paid to a partner for services or capital under IRC §707(c), regardless of partnership profitability — are always subject to self-employment tax for the receiving partner, even a limited partner, to the extent they compensate services. The line between a true limited partner and an active member of an LLC remains a litigated gray area, so substance matters more than the label.

Partner Basis, Distributions, and Loss Limits

Each partner maintains an outside basis in their partnership interest, beginning with capital contributed and increased by their share of income and of partnership liabilities, then decreased by distributions and their share of losses. Basis is the ceiling on deductible losses: a partner cannot deduct losses beyond their basis, with disallowed amounts suspended until basis is restored.

Distributions are generally tax-free to the extent of outside basis and reduce that basis dollar for dollar; only distributions exceeding basis trigger gain. Because partnership liabilities increase basis, debt-financed partnerships can pass through losses that pure equity structures cannot — a meaningful difference for real-estate and capital-intensive ventures.

Allocations and the Partnership Agreement

Partnerships are uniquely flexible because profit and loss need not follow ownership percentages. Special allocations are permitted so long as they have “substantial economic effect” under the §704(b) regulations, which require properly maintained capital accounts and liquidation in accordance with those accounts. This lets partners tailor economics to contribution, risk, or negotiated priority returns.

The partnership agreement is therefore the controlling document for tax allocations, and the IRS will respect it only when its allocations are economically genuine rather than tax-motivated paper entries.

The BBA Centralized Partnership Audit Regime

For tax years beginning after 2017, the Bipartisan Budget Act of 2015 (BBA) replaced the old TEFRA rules with a centralized regime that assesses and collects tax at the partnership level by default. The partnership designates a partnership representative with sole authority to act in an audit, and any imputed underpayment is generally paid by the partnership itself in the adjustment year.

Eligible smaller partnerships may elect out annually, and others may make a “push-out” election to shift adjustments to the partners who were in place during the reviewed year. Because the default places economic responsibility on current partners for prior-year errors, the representative designation and elect-out analysis are now essential parts of every partnership agreement.