A freelance consultant grossing \$80,000 a year asks her tax advisor whether she should set up an S-Corp. The advisor says yes. A second consultant grossing \$180,000 asks the same question and gets the same answer. A third grossing \$40,000 asks and gets the same answer. The advisor charges \$1,800 per year for the S-Corp tax return preparation in each case. For the \$40,000 freelancer, the math on the S-Corp election produces a worse after-tax outcome than the sole proprietorship would have. For the \$80,000 freelancer, the math is roughly break-even. For the \$180,000 freelancer, the S-Corp is a clear win. The choice of entity is not advice that scales linearly with the answer “S-Corp is better”; the answer depends on the income level, and a meaningful share of S-Corp elections are made by filers for whom the math doesn’t actually work.
Most tax-content articles on this topic enumerate the entity-type features (limited liability, pass-through taxation, self-employment-tax treatment) without the actual dollar comparison the choice depends on. The comparison is computable. At three representative income levels, \$40K, \$100K, \$250K of net business income, the comparative math reveals which entity structure produces the best after-tax outcome and at what income threshold the S-Corp election begins to make sense. This article walks the math.
The three structures in tax terms
A sole proprietorship files Schedule C with Form 1040. All net business income flows directly to the owner and is subject to both ordinary income tax and self-employment (SE) tax of 15.3%, 12.4% Social Security (capped at the annual SSA wage base, \$168,600 for tax year 2024, indexed thereafter) and 2.9% Medicare (uncapped, plus 0.9% Additional Medicare Tax on wages above \$200K single / \$250K joint under IRC §3101(b)(2)). The QBI deduction under IRC §199A may apply, subject to its own income thresholds and limitations.
A single-member LLC that has not elected corporate taxation is treated for federal tax purposes identically to a sole proprietorship, same Schedule C, same SE tax. The LLC adds state-law liability protection and entity-level operational flexibility without changing the federal tax math. (Multi-member LLCs file Form 1065 partnership returns by default and have different SE-tax treatment under the partnership rules, but this article focuses on the single-member case typical of the small-business decision.)
An S-Corp, whether organized as a corporation that elects S status or an LLC that elects S-Corp tax treatment under Form 2553, splits the owner’s income into two streams: a W-2 salary subject to FICA payroll taxes (employer + employee portions, equivalent to the 15.3% SE tax) and pass-through distribution income that is subject to ordinary income tax but NOT to SE tax or FICA. The savings is real, but the structure imposes corporate-level administrative costs (separate return Form 1120-S, payroll filings Forms 941 and 940, state corporate franchise taxes in many states) and the reasonable-compensation requirement (covered in the Monday article in this thread).
The math at \$40K net business income
A sole proprietor netting \$40,000:
- SE tax base: \$40,000 × 92.35% = \$36,940 (the SE base is net SE earnings × 0.9235)
- SE tax: \$36,940 × 15.3% = \$5,652
- Ordinary income tax: depends on filing status, other income, deductions; for a single filer with no other income, federal income tax on this amount after standard deduction and SE-tax-deductible-half is roughly \$1,500
- Total federal tax: ~\$7,150
The same income in an S-Corp paying a reasonable salary of \$30,000 (a defensible market rate for a sub-\$50K business; lower than the §1366 reasonable-compensation analysis might support, but illustrative):
- FICA on salary: \$30,000 × 15.3% = \$4,590 (paid through Forms 941 with employer and employee portions combined)
- Distribution: \$10,000 with no SE/FICA tax
- Ordinary income tax on combined \$40,000: roughly \$1,500 (same as above)
- S-Corp administrative cost: \$1,500-\$2,500 in preparation fees and state franchise taxes
- Total: ~\$7,590-\$8,590
The S-Corp election at \$40K of net income costs \$440-\$1,440 more than the sole proprietorship, before accounting for the time cost of running payroll, filing Forms 941 quarterly, and maintaining the corporate formalities. At this income level, the S-Corp is the worse outcome.
The math at \$100K net business income
Sole proprietor:
- SE tax base: \$100,000 × 92.35% = \$92,350
- SE tax: \$92,350 × 15.3% = \$14,130 (Social Security portion is still under the wage-base cap at this level)
- Ordinary income tax: variable, but the federal income tax on this level is materially larger than at \$40K
- Plus the §199A QBI deduction reduces taxable income
S-Corp with a \$60,000 reasonable salary:
- FICA on salary: \$60,000 × 15.3% = \$9,180
- Distribution: \$40,000 with no SE/FICA tax
- SE/FICA savings vs sole prop: roughly \$14,130 – \$9,180 = \$4,950
- S-Corp administrative cost: \$1,500-\$2,500
- Net benefit: \$2,450-\$3,450 per year
At \$100K, the S-Corp election starts to make sense, with the break-even point somewhere between \$50K and \$80K of net business income depending on the specific reasonable salary the §1366 analysis supports and the administrative cost structure in the taxpayer’s state. The savings grow as income grows, because the SE-tax-saved-on-distributions number grows while the administrative cost stays roughly flat.
The math at \$250K net business income
Sole proprietor:
- SE tax: Social Security portion caps at the \$168,600 wage base × 12.4% = \$20,906; Medicare 2.9% on full base \$230,875 = \$6,695; Additional Medicare 0.9% on amount over \$200K wage threshold = roughly \$278; total SE tax ≈ \$27,879
S-Corp with a \$130,000 reasonable salary (in the defensible range for many service businesses at this income level):
- FICA on salary: \$130,000 × 15.3% = \$19,890 (Social Security wage base on \$130K is fully captured; Medicare 2.9% on full \$130K; no Additional Medicare yet)
- Distribution: \$120,000 with no SE/FICA tax
- SE/FICA savings vs sole prop: roughly \$27,879 – \$19,890 = \$7,989
- S-Corp administrative cost: \$1,500-\$2,500
- Net benefit: \$5,489-\$6,489 per year
At \$250K, the S-Corp is clearly the better structure on the SE-tax math alone. Additional benefits accrue from QBI optimization (the salary-vs-distribution split affects the §199A computation), better retirement-plan capacity (the salary supports SEP-IRA, Solo 401(k), and other retirement contribution structures), and the procedural cleanness of a separate employment tax record.
What this means for the entity decision
Three patterns emerge:
Below \$50K net business income, the S-Corp election generally does not produce positive after-tax economics. The sole proprietorship or default-treatment LLC is the right answer.
Between \$50K and \$80K, the math is close enough that the answer depends on the specific facts: the taxpayer’s state (some states impose meaningful franchise taxes on S-Corps), the realistic reasonable salary (a §1366 analysis may support a salary high enough that the savings disappear), the state of the taxpayer’s recordkeeping discipline (S-Corps require ongoing payroll, quarterly filings, and corporate formalities that some taxpayers cannot reliably maintain).
Above \$100K, the S-Corp election usually produces meaningful positive economics, typically \$3K-\$10K+ per year in net SE-tax savings net of administrative cost, with the savings rising as income rises. By \$250K and above, the S-Corp is the default-correct answer for most service-business owners.
The advisor who recommends an S-Corp at every income level is not necessarily wrong on the upper-income clients but is materially wrong on the lower-income clients. The right entity choice is income-level-contingent, and the math is computable from facts the taxpayer already has, net business income, geographic location (state tax structure), and the realistic reasonable-salary range for the role. The decision benefits from being made arithmetically rather than by referral pattern.
Authority: IRC §1361 (S-Corp election eligibility); IRC §1366 (S-Corp pass-through treatment); IRC §1402 (definition of net earnings from self-employment); IRC §3101 (FICA, Social Security and Medicare); IRC §3101(b)(2) (Additional Medicare Tax on wages); IRC §199A (Qualified Business Income deduction); Form 2553 (Election by a Small Business Corporation); Form 1120-S (S-Corp return); Form 941 (Employer’s Quarterly Federal Tax Return); Form 940 (Employer’s Annual Federal Unemployment Tax Return); Schedule C (Form 1040); Schedule SE (Self-Employment Tax); Pub 334 (Tax Guide for Small Business); Pub 542 (Corporations); Pub 533 (Self-Employment Tax, historical, partially superseded); SSA annual wage base announcements; Watson v. Commissioner, T.C. Memo 2012-176 (reasonable-compensation framework, relevant to the salary determination in the S-Corp case).