Small Business Tax Framework & Structure
Small business tax obligations in the United States depend heavily on legal entity classification. Pass-through entities (Sole Proprietorships, LLCs, Partnerships, S-Corporations) pass income directly to owners' personal tax returns, whereas C-Corporations are taxed at the entity level under 26 U.S.C. § 11.
Entity Tax Classification & Filing Requirements
| Entity Type | IRS Tax Form | Taxation Mechanism |
|---|---|---|
| Sole Proprietorship / Single-Member LLC | Form 1040 (Schedule C) | Business income generally reported on the owner's return; self-employment tax may apply to net earnings, generally at 15.3% before applying the Social Security wage-base and other applicable rules. |
| Partnership / Multi-Member LLC | Form 1065 (Schedule K-1) | Pass-through return; owners report K-1 income on Form 1040. |
| S-Corporation | Form 1120-S (Schedule K-1) | Pass-through return; shareholder-employees performing services generally must receive reasonable compensation, with properly treated non-wage distributions generally not subject to self-employment tax. |
| C-Corporation | Form 1120 | 21% flat corporate tax + secondary tax on shareholder dividends. |
Self-Employment Tax & Section 199A QBI Deduction
Two critical tax rules govern pass-through business owners:
- Self-Employment (SE) Tax (IRC § 1401): Self-employed individuals pay 15.3% SE tax (12.4% Social Security + 2.9% Medicare) on 92.35% of net business income. One-half of SE tax is deductible on Form 1040.
- Qualified Business Income (QBI) Deduction (IRC § 199A): Eligible non-corporate taxpayers can generally deduct up to 20% of qualified business income. For 2026, the deduction is permanent, and the §199A threshold and phase-in amounts are $201,750 / $276,750 for most returns and $403,500 / $553,500 for married filing jointly. Additional W-2 wage, qualified-property, specified-service, taxable-income, and other statutory limitations may apply.
2026 Section 199A Thresholds
| Filing Status | Threshold | Phase-In Upper Amount |
|---|---|---|
| Married Filing Jointly | $403,500 | $553,500 |
| Married Filing Separately | $201,775 | $276,775 |
| All Other Returns | $201,750 | $276,750 |
These are 2026 inflation-adjusted §199A amounts. The applicable deduction can be affected by W-2 wages, qualified property, specified service trade or business rules, taxable income, and other statutory limitations.
2026 Self-Employment Tax Numbers
- Regular SE tax rate: 15.3%
- Social Security portion: 12.4%
- Medicare portion: 2.9%
- 2026 Social Security wage base: $184,500
- Net earnings are generally multiplied by 92.35% when computing SE tax.
- One-half of the SE tax is generally deductible as an adjustment to income.
State Tax, Sales Tax & Economic Nexus
Federal tax rules do not determine every state tax obligation. Depending on where a business is organized, operates, owns property, employs people, or makes sales, it may have state income-tax, franchise-tax, sales-tax, use-tax, payroll-tax, registration, and local-tax obligations.
- State income/franchise tax: States use different tax bases, rates, apportionment rules, filing thresholds, and entity-level taxes.
- Sales and use tax: Taxability and registration requirements depend on the state, the product or service, customer location, exemptions, and sourcing rules.
- Economic nexus: Remote sales can create a state sales-tax obligation even without physical presence, but the threshold is state-specific.
- Marketplace sales: Marketplace facilitator laws can shift some collection responsibilities to the marketplace, but businesses still need to understand registration and reporting obligations.
Important: There is no single nationwide state sales-tax threshold. Always check the current rules of the particular state.
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Frequently Asked Questions (FAQ)
A sole proprietorship generally reports business income and expenses on Schedule C attached to Form 1040. A single-member LLC is generally disregarded for federal income-tax purposes unless it elects corporate treatment. A partnership, including an LLC classified as a partnership, generally files Form 1065 and provides Schedule K-1 information to its partners. An eligible S corporation files Form 1120-S and generally passes income, deductions, credits, and other items through to shareholders. A C corporation generally files Form 1120 and is subject to the regular 21% federal corporate income-tax rate.
Under IRC §1401, self-employment tax generally applies to net earnings from self-employment of $400 or more for individuals such as sole proprietors and partners in a partnership, including members of an LLC treated as a partnership, subject to the applicable rules and exceptions. The regular rate is 15.3%: 12.4% for Social Security and 2.9% for Medicare. For 2026, the Social Security wage base is $184,500, while the 2.9% Medicare portion has no wage-base limit. Additional Medicare Tax may also apply above the applicable threshold.
Under IRC §199A, eligible non-corporate taxpayers can generally deduct up to 20% of qualified business income from qualifying trades or businesses, subject to the statutory limitations. For 2026, the deduction has been made permanent. The 2026 §199A threshold amount is $201,750 for most returns and $403,500 for married individuals filing jointly, with phase-in ranges extending to $276,750 and $553,500, respectively. Depending on taxable income and the business, limitations can involve W-2 wages, qualified property, specified service trade or business rules, and the taxable-income limitation. For taxable years beginning after 2025, the law also provides a $400 minimum deduction where the applicable requirements are met and requires at least $1,000 of qualified business income for that minimum-deduction rule.
A sole proprietor generally files Schedule C with Form 1040. A partnership generally files Form 1065 and provides Schedule K-1s to partners. An S corporation generally files Form 1120-S and provides Schedule K-1s to shareholders. A C corporation generally files Form 1120. Employers generally file Form 941 quarterly to report wages and federal employment taxes, but exceptions apply, including certain small employers authorized to file Form 944 annually and agricultural or household employers subject to different reporting rules.
South Dakota v. Wayfair established that a state may require certain remote sellers to collect sales tax based on economic nexus even without physical presence. The actual registration, collection, and filing obligation is state-specific. States use different sales thresholds, transaction thresholds, marketplace rules, exemptions, and sourcing rules, and some states have changed or removed transaction-count tests. A business should therefore check the current rules of each state in which it has potential economic nexus rather than assuming a universal $100,000 or 200-transaction test.
IRC §162 generally permits deductions for ordinary and necessary expenses paid or incurred in carrying on a trade or business, subject to the specific limitations and capitalization rules in the tax code. Common examples can include employee compensation, rent, utilities, software, advertising, business travel, and professional fees when the applicable requirements are satisfied.
For 2026, the §199A threshold is $201,750 for most returns and $403,500 for married individuals filing jointly. The phase-in upper amounts are $276,750 and $553,500, respectively. Married individuals filing separately have a $201,775 threshold and $276,775 phase-in upper amount.
Yes. The One Big Beautiful Bill Act made the 20% QBI deduction permanent for qualifying active trades or businesses. The law also changed the 2026 rules by increasing the income thresholds and adding a $400 minimum deduction for qualifying taxpayers who have at least $1,000 of qualified business income.
For 2026, the maximum amount of combined wages and net self-employment earnings subject to the 12.4% Social Security portion is $184,500. The 2.9% Medicare portion does not have a wage-base limit. Additional Medicare Tax can apply above the applicable statutory threshold.
Not necessarily. The federal tax treatment depends on how the LLC is classified and the member's circumstances. Members of an LLC taxed as a partnership are generally subject to self-employment-tax rules on applicable earnings, while an LLC electing S- or C-corporation treatment follows different rules.
No. Economic-nexus thresholds are state-specific. States can use different sales amounts, transaction counts, marketplace rules, exemptions, and other criteria. A business should check the current rules of each state where it has potential nexus.
Official IRS References
• IRS Publication 334 (Tax Guide for Small Business): irs.gov/p334
• IRS Schedule C Instructions (Profit or Loss From Business): irs.gov/schedulec
• IRS Section 199A Qualified Business Income Deduction: irs.gov/qbi-deduction
• IRS 2026 Estimated Tax / Self-Employment Tax Guidance: irs.gov/p505
• IRS 2026 Form 941 Instructions: irs.gov/form941