Why the K-1 is fundamentally different from a W-2
On a W-2, your employer withholds your taxes and you see the net. On a Schedule K-1 (Form 1065), the partnership reports your allocable share of every income and deduction item — and you owe taxes on that income whether or not the firm paid it out to you. No withholding, no automatic quarterly deposits. You are on your own for funding your tax liability.
Three structural differences that catch new equity partners off guard:
- Income ≠ distributions. Your K-1 shows your share of firm profits. The firm may distribute more or less than that amount. You owe tax on the income figure, not the distribution figure. See Line 19 below.
- March 15 deadline (extendable to September 15). Partnerships must issue K-1s by March 15, but many firms file for extension and issue K-1s in August or September. If your K-1 hasn't arrived by April 15, file a personal extension (Form 4868) to avoid late-filing penalties — even if you can estimate your income and prepay.
- Self-employment tax is additive. Your W-2 showed FICA withholding; as a general partner you now pay both the employee and employer halves of Social Security and Medicare via SE tax. At $184,500 of SE income, the SE tax alone is ~$26,000 before any federal income tax.
The key K-1 lines for Big Law equity partners
Part II — Information about the partner
Box E is your SSN or, if you receive your partnership interest through a professional corporation, the PC's EIN. Box H designates you as a general partner. Box I indicates entity type. If you receive your K-1 through a PC, the PC files its own return and issues a separate return to you — confirm the flow with your tax advisor.
Part III — Income, deductions, credits, and other items
| Line | What it reports | Where it flows on your 1040 |
|---|---|---|
| 1 | Ordinary business income (loss) — your core share of firm profits | Schedule E, Part II → 1040 Schedule E line 28 |
| 4 | Guaranteed payments — fixed income paid regardless of firm profitability; common for income partners and sometimes for equity partners on minimum compensation arrangements | Schedule E, Part II; also included in Line 14a (SE earnings) |
| 5 | Interest income from firm operations (rarely significant at most firms) | Schedule B |
| 11 | Other income items — may include recovery of previously deducted items or other flow-through income | Various, per Box code |
| 12 | §179 deduction — your share of firm equipment and technology depreciation elections | Form 4562, limited by active income and §179 aggregate cap |
| 13 | Other deductions — Box W reports unreimbursed partnership expenses (UPE); other boxes report specific deduction pass-throughs | Schedule E; UPE (Box W) reduces your Schedule E income directly |
| 14 | Self-employment earnings — Box A is the SE tax base. Includes Line 1 (ordinary income) + Line 4 (guaranteed payments), with partnership-level adjustments | Schedule SE → Self-employment tax → 1040 Schedule 2 Line 4 |
| 16 | Foreign transactions — if your firm has London, Hong Kong, or other foreign offices, you may have foreign-source income and foreign taxes paid | Form 1116 (foreign tax credit) or Form 8938 (FATCA) |
| 17 | AMT items — Box A reports AMTI adjustments from accelerated depreciation and other preference items at the firm level | Form 6251 (AMT) |
| 19 | Distributions — this is cash the firm actually paid out to you. It is NOT the same as your taxable income. You may have received $1.2M in distributions but have Line 1 income of only $900K — or the reverse. | Not taxable (it reduces your basis in the partnership interest). Does not appear separately on your 1040. |
| 20Z | §199A information — your allocable share of QBI, W-2 wages, and UBIA of qualified property for the pass-through deduction calculation. Law firms are SSTB, so deduction phases out at higher incomes. | Form 8995-A (SSTB rules apply) |
Self-employment tax: the calculation most new equity partners underestimate
Line 14a flows to Schedule SE, which computes your self-employment tax separately from your income tax. At Big Law income levels, this is a six-figure obligation that you fund entirely through quarterly estimated payments — there is no withholding mechanism.
| Component | Rate | Income range |
|---|---|---|
| Social Security (OASDI) | 12.4% | Up to $184,500 (2026 SS wage base)1 |
| Medicare (HI) | 2.9% | All SE earnings — no cap |
| Additional Medicare Tax | 0.9% | SE income above $200K single / $250K MFJ |
| SE tax deduction | 50% of total SE tax | Above-the-line deduction on Schedule 1 Line 15 |
For a partner with $500K of SE income: SS tax = $22,878 (12.4% × $184,500), Medicare = $14,500 (2.9% × $500K), additional Medicare = $2,700 (0.9% × $300K over threshold). Total SE tax ≈ $40,078. SE deduction = $20,039.
A critical planning note: you have already paid SS tax on wages as an associate. Once your SE income hits the $184,500 SS wage base in the current year, the 12.4% Social Security portion stops. If you had W-2 wages earlier in the year (from a period as a non-equity partner or associate), those wages count toward the $184,500 cap, potentially reducing your SE tax materially.
Interactive SE tax calculator
Estimate your 2026 SE tax from K-1 Line 14a income
If you had W-2 wages earlier in 2026 (e.g., associate period), those reduce the SS wage base available to SE tax.
The §199A QBI deduction: why most equity partners at Big Law firms don't get it
The §199A deduction allows pass-through business owners to deduct up to 20% of their qualified business income. Congress made it permanent under OBBBA (July 2025) and widened the phaseout range. However, law firms are classified as specified service trades or businesses (SSTB) — alongside consulting, financial services, and performing arts — which means the deduction is phased out as your income rises.2
For 2026 (OBBBA-updated rules):
- Below approximately $201,750 (single) / $403,500 (MFJ): full 20% deduction applies
- Phaseout zone (widened to $75,000 under OBBBA): deduction phases from 20% to 0%
- Above approximately $276,750 (single) / $553,500 (MFJ): deduction fully eliminated
Most equity partners at BigLaw firms earn well above the upper threshold — so Box 20Z on your K-1 will show QBI information, but Form 8995-A will produce a zero deduction. The primary exception: years with unusually low income (government transition, medical leave, your departure year) when income drops below the phaseout range. See Roth Conversion Strategy for how these low-income windows interact with Roth planning.
Multi-state K-1 allocation: the hidden state filing obligation
Big Law firms typically have offices in multiple states — New York, California, Illinois, Texas, DC, and elsewhere. The partnership allocates income to each state based on a combination of where the work was performed, where clients are located, and the firm's state-specific apportionment formula (usually payroll, receipts, and property factors).
Your K-1 may include a supplemental schedule showing state-by-state income allocation. Each state with allocated income is a potential non-resident filing obligation:
- New York: Non-resident partners file Form IT-203 for NY-source income. New York uses a receipts-based apportionment formula. Partners resident in NY file IT-201 and claim a credit for other states.
- California: Non-resident partners file Form 540NR. California FTB aggressively audits pass-through income allocations. If your firm had California-source income, you likely have a CA filing obligation even if you never set foot in the state.
- Illinois, New Jersey, Massachusetts, DC: Each state has its own partnership apportionment rules and non-resident partner filing thresholds.
New York applies the convenience of employer rule to partners as well as employees — if you are a New York-resident partner who works remotely from another state, your remote days may still be allocated as New York-source income unless you have a bona fide office outside New York from which the work was required to be performed. For partners at New York firms, this rule can allocate substantial income to New York regardless of where you physically worked. See our dedicated guide at BigLaw Remote Work Taxes: New York's Convenience Rule.
Many equity partners file five or more state returns as a result of multi-state K-1 allocation. Each non-resident return must be filed before your resident state return, which is one more reason most equity partners file extensions.
Unreimbursed partnership expenses (UPE): the deduction most attorneys miss
Line 13, Box W reports your share of the firm's unreimbursed partnership expenses. But there is a separate deduction available to you directly: if you paid business expenses out of pocket as an equity partner that the firm did not reimburse, those are deductible as unreimbursed partnership expenses on your Schedule E.
UPE survives TCJA because it is a partnership expense, not a §67(b) miscellaneous itemized deduction for employees. The key requirement: you must be a general partner (not an employee), the expense must be ordinary and necessary for the partnership's business, and the firm must have a requirement (formal or informal) that partners pay these costs personally.
Common UPE items for Big Law equity partners:
- Bar association dues not reimbursed by the firm
- CLE courses, bar journals, and continuing legal education materials
- Professional liability insurance (tail coverage, individual policy riders)
- Home office costs if you maintain a qualifying home office as a partner
- Business meals at 50% (post-TCJA; entertainment events are 0% deductible even for partners)
- Professional liability insurance premiums (individual policy)
Keep receipts and document that these were not reimbursable under firm policy. The UPE deduction can meaningfully reduce your Schedule E income.
Six costly K-1 filing mistakes equity partners make
- Treating Line 19 distributions as income. Your K-1 income (Line 1 + guaranteed payments) is what you owe taxes on. Distributions (Line 19) reduce your basis in the partnership — they are not additional income. Conflating the two can cause you to overpay or underpay by six figures.
- Ignoring the state K-1 allocation supplement. The one-page federal K-1 is not the whole picture. Most BigLaw firms issue a supplemental schedule showing state-by-state income allocation. Missing a California or New York non-resident return can trigger penalties, interest, and a multi-year examination.
- Missing the UPE deduction entirely. Box 13W is for firm-level UPE. Your personal UPE — bar dues, CLE, home office, professional insurance — is reported directly on Schedule E alongside your K-1 income. Many equity partners never mention these to their accountant, leaving a legitimate deduction on the table.
- Underpaying quarterly estimates in year one of equity partnership. The transition from W-2 to K-1 removes withholding on your largest income stream. Many first-year partners make accurate payments for the first quarter, then forget to scale up as income arrives. SE tax alone can create a $40,000+ additional estimated payment requirement on top of income tax. See Estimated Quarterly Tax Payments.
- Claiming §199A when the SSTB phaseout eliminates it. Most equity partners earn above the phaseout threshold — filing Form 8995-A produces a zero deduction. But if you over-claimed §199A in a prior year, expect to file an amended return. Conversely, if you had a low-income year, you may be leaving a real deduction unclaimed.
- Filing your personal return before your K-1 arrives. Partnerships have until September 15 on extension to issue K-1s. Filing your personal return using an estimated K-1 creates risk — the estimate is almost always wrong. File for a personal extension (Form 4868) by April 15, pay an estimate of what you owe to avoid underpayment interest, and file the actual return once the K-1 arrives.
The K-1 and your estimated tax strategy
Because partnership income has no withholding, you must fund your tax liability through quarterly estimated payments. The IRS safe harbor rule allows you to avoid underpayment penalties by paying the lesser of 90% of current-year tax or 110% of prior-year tax (the 110% rule applies if your prior-year AGI exceeded $150,000).
For most equity partners, the 110% of prior-year rule is the safer approach because current-year income is unpredictable until the firm finalizes distributions. But in a year when income drops significantly (government transition, sabbatical, departure), the 90% of current-year approach can be more accurate and avoid overpayment.
The estimated tax due dates in 2026: April 15, June 16, September 15, and January 15, 2027. For a detailed walkthrough with a quarterly payment estimator, see Estimated Quarterly Tax Payments for Big Law Equity Partners.
Get help navigating your law firm K-1
K-1 reporting, multi-state allocation, UPE deductions, and quarterly estimates are the kind of details that separate advisors who understand Big Law from those who don't. A specialist can review your K-1 alongside your income stack and ensure you're not overpaying or triggering notices.
Related guides
- Equity Partner Tax Planning Guide — SE tax, §199A SSTB phaseout, quarterly estimates, AMT, multi-state nexus
- Estimated Quarterly Tax Payments — safe harbor rules, due dates, variable income problem
- Attorney Tax Deductions — what you can and cannot deduct as a partner vs. W-2 associate
- BigLaw Remote Work Taxes — New York's convenience rule, state allocation, domicile changes
- First Year Equity Partner Financial Planning — month-by-month guide to the SE tax shock, capital contribution, and NQDC election
- Roth Conversion Strategy — using low-income windows to convert when the §199A phase-out doesn't apply
Sources
- Social Security Administration, "Contribution and Benefit Base 2026." 2026 SS wage base: $184,500. ssa.gov/oact/cola/cbb.html.
- IRC §199A — Deduction for Qualified Business Income. SSTB classification for law firms per Treas. Reg. §1.199A-5. Phaseout thresholds per IRS Rev. Proc. 2025-32; OBBBA (July 2025) widened phaseout range to $75,000 (single) and made the deduction permanent. irs.gov/newsroom/qualified-business-income-deduction.
- IRS Publication 541 — Partnerships. Covers K-1 reporting requirements, partner SE tax, UPE deductions, and basis tracking. irs.gov/publications/p541.
- IRS Form 1065 Schedule K-1 and Instructions for Schedule K-1 (Form 1065). irs.gov/forms-pubs/about-schedule-k-1-form-1065.
- IRC §1402 — Definitions of net earnings from self-employment. Partner SE tax base computation including guaranteed payments. law.cornell.edu/uscode/text/26/1402.
Tax values verified for 2026: SS wage base $184,500 per SSA; §199A thresholds per IRS Rev. Proc. 2025-32 and OBBBA (July 2025); SE tax rates per IRC §1401.