Small Business Tax Filing Guide 2026
Complete guide to filing taxes for small businesses: sole proprietors, LLCs, S-corps, and self-employed individuals. Deductions, forms, deadlines, and quarterly payment requirements.
Filing small business taxes requires understanding your business structure, tracking deductible expenses, and meeting quarterly payment obligations. This guide covers the essentials for every common business type.
Use our Self-Employed Tax Calculator to estimate your self-employment tax. For deduction details, see Tax Deductions List and Home Office Deduction Guide.
Filing by Business Structure
Sole Proprietorship / Single-Member LLC: Report business income and expenses on Schedule C (line 1 for gross receipts, lines 8-27 for expenses). Net profit flows to Form 1040 line 3 and Schedule SE for self-employment tax. Partnerships / Multi-Member LLCs: File Form 1065 informational return and issue Schedule K-1 to each partner. S-Corporations: File Form 1120-S, issue Schedule K-1 to shareholders. C-Corporations: File Form 1120, pay corporate tax rates.
Before filing taxes, many small businesses need to apply for an Employer Identification Number (EIN) — the federal tax ID used to identify your business entity to the IRS.
Key Business Deductions
The most valuable deductions for small businesses include: home office (regular method or simplified $5/sq ft, max 300 sq ft), vehicle expenses (standard mileage 67 cents/mile for 2025, or actual expenses), health insurance premiums (deductible as adjustment to income), retirement contributions (SEP IRA up to 25% of compensation, Solo 401k up to $70,000 for 2025), supplies and equipment, software and subscriptions, professional fees (accountant, lawyer), business travel and meals (50% of meals), and marketing and advertising. See our Home Office Deduction guide for detailed requirements.
Quarterly Estimated Tax Payments
If you expect to owe $1,000 or more when you file, you must make quarterly estimated tax payments using Form 1040-ES. Due dates: April 15, June 15, September 15, and January 15. Pay online via IRS Direct Pay or the Electronic Federal Tax Payment System (EFTPS). The penalty for underpayment of estimated tax is calculated on Form 2210. Use our Estimated Tax Payments guide for detailed instructions.
Required Forms and Deadlines
Individual + Business (Sole Prop/SMLLC): April 15, 2026. Partnerships/S-Corps: March 15, 2026. C-Corps: April 15, 2026. Automatic 6-month extension available via Form 7004. You may also need Form 941 (quarterly payroll), Form 940 (annual unemployment), Form W-2/W-3 (employee wages), and Form 1099-NEC (contractor payments over $600).
Employers must file Form 941 each quarter to report wages, tips, Social Security, Medicare, and federal income tax withheld from employee paychecks.
Frequently Asked Questions
Sole prop: Schedule C + Form 1040. Partnership: Form 1065. S-corp: Form 1120-S. C-corp: Form 1120. All pay self-employment tax on net earnings.
Home office, vehicle, health insurance, retirement contributions, supplies, software, travel, meals (50%), professional fees, marketing.
April 15, June 15, September 15, January 15. Required if you expect to owe $1,000+. Use Form 1040-ES.
15.3% total: 12.4% Social Security (up to $176,100 for 2025) + 2.9% Medicare (no cap). Deduct half as adjustment.
Sole prop: April 15. Partnership/S-corp: March 15. C-corp: April 15. File Form 7004 for extension.
All business filing requirements, deduction rules, and deadlines verified against IRS publications for the 2025-2026 tax year.