The bottom line

A Schedule K-1 reports your share of income, deductions, and credits from a pass-through entity — a partnership, an S-corporation, or a trust. The entity itself doesn't pay federal income tax; it allocates everything to its owners and they pay tax individually. That's why K-1 holders get taxed on income they may not have actually received as cash. K-1s land in March or April, often after April 15, forcing extension filings. The key fields are not just the income boxes — they're the basis-tracking lines (especially section L for partnerships) that govern how much of an eventual sale is taxable, and Box 20 with the Section 199A QBI flags that drive a large potential deduction. K-1s from publicly-traded partnerships (PTPs / MLPs) follow the same format but trigger UBTI in retirement accounts and require state filings everywhere the PTP operates.

What entities issue K-1s

Three federal forms produce K-1s:

  • Form 1065 K-1 — issued by partnerships (general, limited, LLP) and most multi-member LLCs (which default to partnership taxation).
  • Form 1120-S K-1 — issued by S-corporations.
  • Form 1041 K-1 — issued by estates and trusts to beneficiaries.

The three are similarly structured but have different boxes. This guide focuses on the Form 1065 K-1 (partnership), the most common, and notes 1120-S differences inline.

Why K-1s arrive late

The partnership has to close its books, prepare Form 1065, and issue K-1s to every partner. The legal deadline is 15 March (calendar-year partnerships). Many partnerships file extensions, pushing K-1 issuance to 15 September. Some PTPs are notorious for late issuance — investors with a single MLP holding sometimes wait until late August to file their own 1040.

If you have an investment that issues K-1s, plan to file your own extension (Form 4868) by 15 April. The extension is automatic but you still owe the tax by April — estimate using your prior-year K-1 numbers if the current year's hasn't arrived.

The fields that matter

Part I — Information about the partnership

Boxes A–C: partnership name, address, EIN. Note this — you'll need the EIN if the partnership has nexus in multiple states.

Part II — Information about the partner

Boxes E–F: your name, address. Box G: partner type (general / limited / LLC member). Box H: domestic / foreign partner (foreign partners face different rules). Box I1–I2: the type of partner — individual, corporation, trust, IRA, etc. Critical for IRAs and retirement accounts. Box J: profit / loss / capital sharing percentages — your slice. Box K: liability share. This is part of basis tracking; pay attention.

Section L — Partner's capital account analysis

This is the most important section for long-term investors. It tracks:

  • Beginning capital
  • Capital contributed
  • Current year increase / decrease
  • Withdrawals & distributions
  • Ending capital

Capital account is not the same as basis. Basis includes share of liabilities; capital account doesn't. Both matter and both must be tracked across years.

If you sell or redeem your partnership interest, your taxable gain / loss is proceeds − basis. If you don't track basis correctly, you risk paying tax on amounts you've already paid tax on, or vice versa.

Part III — Partner's share of current year income, deductions, credits

The income boxes:

  • Box 1: Ordinary business income or loss. Goes on Schedule E (1040).
  • Box 2: Net rental real estate income/loss.
  • Box 3: Other net rental income.
  • Box 4: Guaranteed payments (analogous to wages for partners).
  • Box 5: Interest income.
  • Box 6a/6b/6c: Ordinary, qualified, and dividend-equivalent dividends.
  • Box 7: Royalties.
  • Box 8/9a/9b: Net short-term gain, long-term gain, collectibles gain.
  • Box 10: Net §1231 gain (depreciable business property).
  • Box 11: Other income / loss with a code letter (B = involuntary conversions, C = §1256 contracts, F = section 743(b) adjustment, etc.).
  • Box 13: Deductions (charitable contributions, §179 expense, investment interest, etc.).
  • Box 14: Self-employment earnings (general partners).
  • Box 19: Distributions of money or property — does not affect this year's taxable income (tax was paid via the income boxes); reduces capital account / basis.
  • Box 20: Other information including Section 199A codes (Z, AA, AB, AC, AD) for the QBI deduction.

The boxes don't go directly to your 1040 — they go to various schedules:

  • Box 1 → Schedule E Part II
  • Box 5 → Schedule B
  • Box 6a → Schedule B (qualified dividends → 1040 line 3a)
  • Box 8/9a → Schedule D / Form 8949
  • Box 10 → Form 4797
  • Box 13 codes → various places per the K-1 codes
  • Box 19 → not currently taxable, used for basis tracking
  • Box 20 codes → Form 8995 / 8995-A (QBI)

The Section 199A QBI deduction

If Box 20 has codes Z, AA, AB, AC, AD, the partnership is reporting figures you need to compute the 20% Qualified Business Income deduction under §199A. This is a deduction of up to 20% of qualified business income, with phase-outs and limitations for "specified service trades or businesses" (SSTBs — health, law, consulting, finance) above income thresholds (~$200k single / $400k MFJ for 2026).

For a passive K-1 holder in a manufacturing or real-estate LP, you may be able to deduct 20% of Box 1 ordinary business income — a meaningful tax saving. For an SSTB partnership above the threshold, the deduction phases to zero.

Form 8995 (simplified) or 8995-A (full) computes the deduction. Tax software handles this if you enter the K-1 codes correctly.

The basis-tracking nightmare

Every year your partnership interest's basis changes:

  • Increases by: capital contributions, your share of partnership income, share of partnership liabilities.
  • Decreases by: distributions to you, your share of partnership losses, share of liabilities you're relieved from.

Basis can never go below zero. If your share of losses + distributions exceeds basis, you can only deduct losses up to basis — the rest carry forward. Distributions in excess of basis become taxable gain.

You must track basis across years. The partnership doesn't always do this for you; partnerships started before 2018 typically didn't, and some still don't. Keep a running spreadsheet from the day you invest. If you sell years later without correct basis, you'll either over- or under-pay tax — and an IRS audit can extract the difference plus penalties up to 6 years back.

PTPs and MLPs — the special case

Publicly-traded partnerships (PTPs) — most commonly Master Limited Partnerships (MLPs) in energy / pipelines / real estate — issue K-1s in the same format. Three special wrinkles:

  1. State filing requirements: a PTP operating in 30 states attributes income to those states. Technically you owe state income tax filings in each. Most retail K-1 investors ignore this for tiny dollar amounts; the underlying obligation still exists.

  2. UBTI in retirement accounts: PTPs can generate Unrelated Business Taxable Income, which is taxable to an IRA above the $1,000 threshold. Holding MLPs inside an IRA can trigger an unexpected tax bill. Generally, hold MLPs in taxable accounts only.

  3. Recharacterization on sale: when you sell a PTP, part of the gain is recharacterized as ordinary income (recapture of past depreciation deductions) rather than capital gain. The PTP issues a "sales schedule" with the K-1 to compute this — easy to miss.

The combination — late K-1, multi-state filing, UBTI risk, recharacterization — is why financial advisors often steer retail investors toward 1099-DIV-issuing dividend ETFs instead of MLPs. The yield difference rarely justifies the complexity.

Worked example

You bought a $50,000 limited-partner interest in a real-estate LP. After 3 years you receive your year-3 K-1:

  • Box 1 (ordinary business income): $0 (the LP is depreciating heavily)
  • Box 2 (rental income): −$8,000 (depreciation-driven loss)
  • Box 19A (cash distribution): $4,500
  • Box 20 Z (199A QBI): not applicable for rental real estate that doesn't reach trade-or-business standard; check.

Tax impact this year:

  • Net rental loss flows to Schedule E. With $8,000 loss and $4,500 cash received, you might think you're net negative — but basis accounting changes this picture.
  • Distribution of $4,500 is not taxable this year; it reduces your basis.
  • Loss of $8,000 also reduces your basis.

Basis tracking:

  • Start year 3 basis: $42,000 (after years 1–2 reductions).
  • Less year 3 loss: $42,000 − $8,000 = $34,000.
  • Less year 3 distribution: $34,000 − $4,500 = $29,500.
  • End year 3 basis: $29,500.

The $8,000 rental loss can be deducted against your other passive income (or carried forward if you have none — passive activity loss rules under §469). A typical investor uses Form 8582 to compute the allowed deduction.

When you eventually exit — sell your LP interest for $55,000 — your gain is $55,000 − $29,500 = $25,500. Some of that may be recharacterized as ordinary income (depreciation recapture). The exit K-1 will include the recapture computation.

Practical takeaways

  • File extension every year you have an open K-1 investment. Form 4868 is automatic; just send it.
  • Track basis from day one. Spreadsheet, dedicated software, or a CPA — but track. Don't rely on the partnership to remember.
  • Don't put MLPs in IRAs. UBTI risk + tax-deferred wrapper makes no sense.
  • Read Box 20 codes carefully. The QBI deduction can be worth thousands. Codes get scrambled if you transcribe by hand; upload the K-1 to tax software when possible.
  • Multi-state K-1 income is a real obligation. Most retail investors ignore it for tiny amounts, but be aware of the rule.
  • K-1 distributions are not taxable income. They look like dividends to the untrained eye. They aren't — the income is reported separately in Boxes 1–11; the cash distribution is just a return of capital that reduces basis.
  • If you don't enjoy reading IRS forms, K-1s might not be your asset class. This is a serious recommendation, not a joke.

K-1s are the price of admission for direct investment in real estate, private equity, hedge funds, and energy partnerships. They demand attention. The investors who ignore them silently overpay tax for years; the ones who track basis correctly and file on time keep what's theirs.