Schedule C vs K-1: Self-Employment Tax, QBI, and Basis Limits

Choosing between Schedule C and Schedule K-1 isn’t really a choice — your business structure decides for you. Sole proprietors and single-member LLCs report business profit on Schedule C as part of their personal Form 1040. Partnerships, multi-member LLCs, and S corporations file their own returns and issue a Schedule K-1 to each owner. The form matters because the tax treatment behind each one is very different, and the gap in self-employment tax alone can run into thousands of dollars a year.

Which Form Your Entity Uses

You don’t pick the form. Your legal structure picks it for you.

You can change the default. A single-member LLC can elect corporate taxation with Form 8832, and either a corporation or an LLC that has elected corporate status can then elect S corporation treatment by filing Form 2553 within two months and 15 days of the start of the tax year.6Internal Revenue Service. About Form 8832, Entity Classification Election That election changes which form you use, and it changes how the income gets taxed.

How Schedule C Works

Schedule C is a profit-and-loss statement built into your personal return. You start with gross receipts, subtract cost of goods sold for gross profit, and then deduct ordinary business expenses like supplies, advertising, insurance, and vehicle costs. The net profit or loss flows directly onto Form 1040 as part of your adjusted gross income.7Internal Revenue Service. Self-Employed Individuals Tax Center

The simplicity is the appeal. No separate business return, no K-1 to wait for, no formal entity to maintain. The catch is that every dollar of that net profit is subject to both income tax and self-employment tax.

How Schedule K-1 Works

A K-1 is a reporting document the partnership or S corporation issues to each owner after the entity files its own return. It shows your share of the entity’s income, deductions, credits, and other tax items. You then report those amounts on Schedule E of your Form 1040.8Internal Revenue Service. S Corporations

The entity itself doesn’t pay federal income tax. Everything passes through to the owners at their individual rates, which sidesteps the double taxation that hits C corporations.8Internal Revenue Service. S Corporations

One feature surprises new K-1 recipients: you owe tax on your share of the entity’s income for the year it was earned, whether or not the entity actually distributed cash. If a partnership earns $200,000 and your share is 50%, you owe tax on $100,000 even if you never saw a dollar of it. That mismatch between taxable income and cash in hand bites hardest in the early years, when a growing business is reinvesting profits.

Self-Employment Tax: Where the Money Is

This is the difference that drives most restructuring decisions.

Schedule C

Every dollar of Schedule C net profit is subject to self-employment tax, which covers Social Security and Medicare at a combined 15.3% — 12.4% for Social Security and 2.9% for Medicare.9Internal Revenue Service. Self-Employment Tax (Social Security and Medicare Taxes) It applies to 92.35% of your net earnings, not the full amount, because the IRS adjusts for the employer-equivalent portion first.10Internal Revenue Service. Topic No. 554, Self-Employment Tax

The 12.4% Social Security piece only applies to earnings up to $184,500 in 2026; income above that threshold escapes it. The 2.9% Medicare piece has no cap. An Additional Medicare Tax of 0.9% kicks in on self-employment income above $200,000 for single filers or $250,000 for joint filers.11Internal Revenue Service. Questions and Answers for the Additional Medicare Tax You can deduct the employer-equivalent half of your SE tax when calculating AGI, which cuts your income tax but does nothing to the SE tax itself.9Internal Revenue Service. Self-Employment Tax (Social Security and Medicare Taxes)

Partnership K-1

SE tax treatment for partners depends on your partner status. General partners owe SE tax on their distributive share of partnership income, just like a sole proprietor. Limited partners are exempt from SE tax on their share of ordinary income under IRC Section 1402(a)(13). The one exception cuts across both: guaranteed payments for services rendered to the partnership are always subject to SE tax, whatever kind of partner you are.12Internal Revenue Service. Self-Employment Tax and Partners

S Corporation K-1

Ordinary business income flowing through an S corporation K-1 isn’t subject to self-employment tax at all. That’s the whole appeal of the S election. The trade-off: if you perform services for the S corporation, it has to pay you a reasonable salary through W-2 payroll, and that salary bears the full 15.3% FICA tax, split between you and the corporation.13Internal Revenue Service. S Corporation Employees, Shareholders and Corporate Officers Only the income above that salary, taken as distributions, escapes employment taxes.

A concrete comparison: a business that nets $150,000 as a sole proprietorship exposes roughly the whole $150,000 to SE tax. Run the same numbers through an S corporation with an $80,000 reasonable salary, and only the $80,000 bears FICA. The remaining $70,000 in distributions avoids employment taxes. The savings can easily exceed $10,000 a year, which is exactly why the IRS pays attention to the salary figure.

The Reasonable Compensation Catch

You cannot pay yourself an artificially low salary just to shrink payroll taxes. Courts have held that shareholder-employees who provide more than minor services must receive wages, and payments dressed up as distributions or “management expenses” still count as compensation.13Internal Revenue Service. S Corporation Employees, Shareholders and Corporate Officers

The IRS looks at several factors when assessing whether a salary is reasonable:14Internal Revenue Service. S Corporation Compensation and Medical Insurance Issues

  • Wages paid by comparable businesses for comparable services
  • Your training and experience
  • The time and effort you actually put into the business
  • Your duties and responsibilities
  • Dividend history, particularly whether distributions dwarf salary
  • What non-shareholder employees earn for similar work

Getting this wrong is expensive. If the IRS reclassifies distributions as wages, you owe back payroll taxes plus penalties and interest.

The QBI Deduction Applies to Both

Schedule C filers and K-1 recipients can both claim the Section 199A Qualified Business Income deduction of up to 20% of qualified business income from a pass-through or sole proprietorship.15Office of the Law Revision Counsel. 26 USC 199A – Qualified Business Income The One Big Beautiful Bill Act made the deduction permanent starting in 2026.

At lower income levels the deduction is straightforward — 20% of qualified business income, capped at 20% of taxable income. At higher levels, limitations kick in. For 2026, the deduction begins phasing out for specified service trades or businesses (law, medicine, consulting, financial services, and similar fields) once taxable income reaches $200,000 for single filers or $400,000 for joint filers. Above $275,000 single or $550,000 joint, the deduction disappears entirely for those service businesses. Non-service businesses face a separate set of limits tied to W-2 wages paid and the depreciable basis of qualified property, but only above the same income thresholds. QBI reduces income tax; it does not reduce self-employment tax.

Basis Limits on K-1 Losses

K-1 recipients face a layer Schedule C filers don’t: you can only deduct losses up to your basis in the entity. Basis is your investment in the business, adjusted over time — original contributions plus accumulated income, minus distributions and prior loss deductions.

Partnership Basis

A partner’s share of partnership losses is deductible only to the extent of their outside basis at year-end. Anything above that carries forward until you have basis to absorb it.16Internal Revenue Service. New Limits on Partners Shares of Partnership Losses Frequently Asked Questions Partners also have to clear the at-risk and passive activity rules, applied in sequence; failing any one suspends the deduction.

S Corporation Basis

S corporation shareholders track stock and debt basis on Form 7203. Stock basis starts with what you paid, rises with income allocations and additional contributions, and falls with distributions and loss deductions. An important distinction from partnerships: only loans you personally made to the corporation increase your debt basis. Guaranteeing a bank loan does not, which catches many S corporation owners trying to deduct losses. The IRS recommends maintaining Form 7203 every year, even in years you aren’t required to file it, so basis stays consistent.17Internal Revenue Service. Instructions for Form 7203

Deadlines and Estimated Payments

Filing deadlines vary by form, and pass-through penalties are steeper than most owners expect.

  • Schedule C is part of Form 1040, due April 15 for calendar-year filers, with a six-month extension available to October 15.
  • Form 1065 for partnerships is due March 15, with a six-month extension to September 15.18Internal Revenue Service. Publication 509 (2026), Tax Calendars
  • Form 1120-S for S corporations is also due March 15, with the same six-month extension option.18Internal Revenue Service. Publication 509 (2026), Tax Calendars

Late filing penalties for partnerships and S corporations run per owner, per month. For returns due after December 31, 2025, the penalty is $255 per partner or shareholder for each month or partial month the return is late, up to 12 months.19Internal Revenue Service. Failure to File Penalty A four-shareholder S corporation that files three months late faces $3,060 in penalties. The charge applies even if the entity owes no tax of its own.

Pass-through income doesn’t have taxes withheld, so quarterly estimated payments are your responsibility if you expect to owe $1,000 or more. The 2026 deadlines are April 15, June 15, September 15, and January 15, 2027.20Taxpayer Advocate Service. Making Estimated Payments Missing one triggers an underpayment penalty unless you clear a safe harbor: total payments covering at least 90% of the current year’s tax or 100% of the prior year’s tax (110% if prior-year AGI exceeded $150,000).21Internal Revenue Service. Underpayment of Estimated Tax by Individuals Penalty

S corporation shareholder-employees have a partial advantage. Income and FICA withheld from their W-2 wages count toward their annual tax obligation, and because withholding is treated as paid evenly throughout the year regardless of when it actually happened, increasing withholding late in the year can rescue an owner who missed or underpaid earlier quarters.