Self-Employment Tax in 2026: Calculate It and Reduce Costs Correctly

Self-employment tax has two main components: 12.4% Social Security and 2.9% Medicare. For 2026, the Social Security earnings ceiling is $184,500, shared with covered wages. Medicare has no equivalent ceiling, and Additional Medicare Tax can apply above separate filing-status thresholds. The familiar 15.3% is therefore not a flat tax on every dollar of business revenue. IRS self-employment tax guidance

Start with allowable business expenses and accurate records, then compare retirement deductions and entity choices separately. Expenses can reduce the profit subject to self-employment tax; owner retirement and health-insurance deductions generally operate elsewhere on the return. Rules were checked November 3, 2026, and examples use an ordinary Schedule C business unless stated otherwise.

Start with the right earnings base

Net business profit is revenue minus allowable business expenses. Generally, 92.35% of that profit enters the self-employment tax calculation. Net self-employment earnings of $400 or more generally trigger Schedule SE, subject to special rules. IRS Topic 554

For a hypothetical $150,000 profit, with no other covered wages:

Calculation	Amount
Profit × 92.35%	$138,525.00
Social Security: $138,525 × 12.4%	$17,177.10
Medicare: $138,525 × 2.9%	$4,017.23
Combined self-employment tax, rounded	$21,194.33
Employer-equivalent deduction, approximately	$10,597.16

The employer-equivalent deduction reduces adjusted gross income for income-tax purposes; it does not reduce this self-employment tax calculation. Additional Medicare Tax is 0.9% above combined earnings thresholds of $200,000 for single filers, $250,000 for married filing jointly and $125,000 for married filing separately, with coordination for wages. IRS self-employment tax guidance

If you also have a job, supply the preparer with your W-2 before estimating the Social Security portion. Applying the full $184,500 ceiling separately to wages and business earnings can overstate the tax.

Claim eligible business expenses and keep the records

An allowable Schedule C expense can reduce the profit subject to both income and self-employment tax. Below the Social Security ceiling, a $1,000 reduction in profit reduces the ordinary self-employment tax by about $141.30: $1,000 × 92.35% × 15.3%. Income-tax effects are additional and depend on the rest of the return.

Spending $1,000 solely to obtain that deduction still costs money. Start with expenses already incurred for the business: software, supplies, professional services and properly documented business travel. Keep business purpose, invoices and payment records together rather than relying on a bank transaction description.

For eligible business vehicle use, the 2026 standard mileage rate is 72.5 cents for January–June and 76 cents for July–December. With 2,000 qualifying miles in each period, the deduction is $1,450 + $1,520 = $2,970. Separate business trips from personal commuting and apply the chosen vehicle-expense method consistently. IRS mileage rates, vehicle-expense rules.

A qualifying home office may use the simplified $5-per-square-foot method, up to 300 square feet, subject to eligibility and income limits. The simplified method does not remove the regular and exclusive business-use requirements applicable to an ordinary office. A 200-square-foot qualifying office yields a $1,000 starting calculation, not a deduction for the entire home’s expenses. IRS simplified home-office method

Separate owner deductions from Schedule C expenses

A sole proprietor’s own deductible retirement contributions generally go on Schedule 1, not Schedule C. The self-employed health-insurance deduction also follows separate eligibility and income limits; it is not ordinarily a reduction of Schedule C profit or current self-employment earnings. IRS owner retirement-contribution guidance and IRS explanation of Section 162(l)

Include these deductions in the income-tax estimate and label where each enters the return. Maintain separate subtotals for Schedule C expenses, the employer-equivalent self-employment-tax deduction, owner retirement contributions, and eligible health insurance. That structure makes their different effects visible.

Calculate retirement contributions with the self-employed formula

A one-participant 401(k) can combine employee deferrals with an employer contribution. It generally covers an owner with no employees, or the owner and spouse. Having eligible employees can change the plan’s obligations. IRS one-participant 401(k) guidance

For 2026, the standard employee deferral limit is $24,500 and the overall defined-contribution limit is $72,000 before permitted catch-up contributions. A stated 25% employer contribution rate translates to a 20% calculation for a self-employed owner’s adjusted earnings under the applicable worksheet; it is not simply 25% of Schedule C profit. IRS 2026 limits and SEP contribution limits

For an owner under 50 with $100,000 Schedule C profit, no other wages or plan deferrals, and a plan using that employer rate:

Ordinary self-employment tax is approximately $14,129.55.
Subtract half, $7,064.78, for adjusted earnings of approximately $92,935.23.
Multiply by 20% for an employer contribution of approximately $18,587.05.
An eligible solo 401(k) could add $24,500 of employee deferrals, totaling approximately $43,087.05 before any other limits or adjustments.

A SEP’s employer contribution in this example is approximately $18,587.05. SECURE 2.0 also permits Roth SEP contributions; check whether the chosen provider offers them and how they will be reported and taxed. IRS Roth SEP guidance.

Compare an S corporation using total costs

An S corporation must pay reasonable compensation for an owner-employee’s services before treating payments as nonwage distributions. There is no IRS-approved rule that salary should equal 40%, 50% or another fixed share of profit. Duties, time, experience and comparable compensation matter. IRS reasonable-compensation guidance

Consider $200,000 of business profit before owner compensation and employer payroll taxes, with no outside wages. A sole proprietor’s ordinary self-employment tax is about $28,234.30. In a hypothetical S corporation where $100,000 is independently supported as reasonable salary:

Item	Illustrative amount
Owner salary	$100,000
Employer Social Security and Medicare	$7,650
Employee Social Security and Medicare	$7,650
Remaining business profit before other costs	$92,350
Combined employer and employee FICA	$15,300

The modeled payroll-tax difference is $12,934.30. Subtract payroll administration, tax preparation, unemployment taxes, and state charges, then compare income-tax effects and retirement contributions. The S corporation retains $92,350 before other costs after paying the $100,000 salary and $7,650 employer FICA. Support the salary independently from duties and comparable pay before relying on the calculation.

Obtain a written all-in comparison before electing. The business entity guide explains the distinction between forming an LLC and choosing a tax classification.

Apply QBI and family-employment rules accurately

The qualified business income deduction affects income tax, not the self-employment tax base. QBI generally reflects allocable deductions such as the deductible portion of self-employment tax, owner health insurance and retirement contributions. It is not automatically 20% of gross receipts or unadjusted profit. IRS QBI guidance

For 2026, the limitation phase-in runs from $201,750 to $276,750 for single and most other returns, $403,500 to $553,500 for joint returns, and $201,775 to $276,775 for married filing separately. These are taxable-income thresholds before the QBI deduction, not business revenue. Specified service businesses and wage/property limits require separate analysis. A new $400 minimum deduction can apply with at least $1,000 of qualifying active-business QBI and the required participation. IRS Revenue Procedure 2025-32

For genuine work in a parent’s sole proprietorship, or a partnership where every partner is the child’s parent, wages paid to a child under 18 are generally exempt from Social Security and Medicare; the FUTA exemption extends to under 21. Corporate employment generally does not receive those exemptions. Income-tax withholding rules still apply, and labor laws and reasonable pay must be respected. IRS family employees

Keep a payment calendar alongside the deductions

For most calendar-year taxpayers, 2026 estimated payments fall on April 15, June 15, September 15 and January 15, 2027, subject to applicable relief and exceptions. Estimated payments cover income tax and self-employment tax; paying an estimate is not itself a business deduction. IRS Publication 505

Update the forecast when profit changes. Keep a reserve based on the combined tax estimate rather than assuming that 15.3% alone covers the bill. Before year-end, reconcile expense records, retirement eligibility and any payroll election with your preparer.

Sources

Rules checked November 3, 2026 using the linked IRS materials, including self-employment tax, 2026 mileage rates, reasonable compensation, and QBI. Each example states the earnings, wage, or contribution assumptions used.