A Simple Guide to Filing Small Business Taxes: Forms and Deadlines

Quick overview

Small business taxes cover a range of returns and payments: an annual income tax return for the business or owner, payroll (withholding) taxes if you have employees, estimated tax payments for owner income not subject to withholding, and information returns for contractors. Which forms you file depends on how your business is structured and whether you have employees or independent contractors.

This guide explains the common forms, standard federal deadlines, practical recordkeeping and filing tips, and common mistakes to avoid. For a concise checklist focusing on filing, withholding, and recordkeeping, see our internal checklist: Small Business Compliance: Filing, Withholding and Recordkeeping Checklist.

Which federal forms are most common?

• Schedule C (Form 1040): Sole proprietors report business income and expenses on Schedule C attached to the owner’s Form 1040. See IRS guidance: Small Businesses & Self-Employed.
• Form 1065 (Partnership): Partnerships file Form 1065 to report income, deductions, gains and losses; partners receive K-1s showing their share.
• Form 1120 (C Corporation): Used by C corporations to report corporate income and calculate corporate tax.
• Form 1120-S (S Corporation): S corps use Form 1120-S and issue Schedule K-1s to shareholders reporting pass-through income.
• Form 941 and Form 940: Payroll tax forms. Form 941 reports quarterly federal payroll taxes (income tax withheld, Social Security and Medicare), and Form 940 reports annual Federal Unemployment Tax Act (FUTA) tax.
• Schedule SE: Self-employment tax for sole proprietors and partners.
• Form 1099-NEC: Report payments of $600+ to nonemployee contractors. Also issue W-2s to employees (reported to SSA/IRS).
• Form 1040-ES: Estimated tax payment vouchers for individuals (including many sole proprietors) to pay quarterly estimated taxes.

Authoritative IRS pages for these forms are linked throughout the IRS Small Businesses portal: https://www.irs.gov/businesses/small-businesses-self-employed.

Typical federal deadlines (general rules)

• March 15: Partnerships (Form 1065) and S corporations (Form 1120-S) generally file by March 15 of the tax year following the tax year. (File Form 7004 to request an automatic extension.)
• April 15: Individual returns (Form 1040 and Schedule C) and C corporations (Form 1120) usually are due by April 15. If April 15 falls on a weekend or holiday the IRS moves the due date accordingly.
• Quarterly estimated tax payments: generally due April, June, September and January (for the following year’s 4th quarter). See IRS estimated tax guidance: https://www.irs.gov/businesses/small-businesses-self-employed/estimated-taxes.
• Payroll deposits and returns: deposit schedules vary by tax liability (semiweekly or monthly) and must be followed precisely; Form 941 is filed quarterly.

Note: Filing an extension (Form 4868 for individuals; Form 7004 for many business entities) extends the time to file but not the time to pay. You must estimate and pay any tax due by the original deadline to avoid late-payment penalties and interest. See IRS forms and instructions.

Practical filing timeline and checklist (owner perspective)

1. Year-round: Keep records, separate business and personal accounts, reconcile bank and credit card statements monthly, and update bookkeeping software (QuickBooks, Xero, etc.).
2. Jan–Feb: Collect 1099s, W-2s, year-end payroll reports, and review last year’s estimated tax payments. Request missing contractor W-9s early.
3. Feb–Mar: If you are a partnership or S corp, prepare K-1s and file by March 15 (or file Form 7004 for extension).
4. Mar–Apr: Finish owner/individual tax preparation; pay any balance due by April 15 (or request extension with Form 4868). If you file for extension, plan for an October filing date but pay by April 15.
5. Quarterly: Make estimated tax payments on the due dates and deposit payroll taxes on the schedule assigned to your business.
6. After filing: Keep tax returns and supporting records for at least three years; keep payroll records longer. The IRS suggests longer retention for matters involving substantial underreporting—review IRS recordkeeping guidance.

Common small-business mistakes and how to avoid them

• Treating owner and business funds as interchangeable: Use a separate bank account and credit card for business transactions. This simplifies bookkeeping and strengthens liability protection.
• Missing contractor documentation: You need a W-9 before paying a contractor; file 1099-NEC for qualifying payments and file them on time.
• Ignoring payroll deposit schedules: Payroll taxes have strict deposit schedules—missing a deposit can create steep penalties.
• Filing late without paying: An extension to file does not extend time to pay. Estimate and pay to reduce penalties.
• Poor recordkeeping: Receipts, mileage logs, and supporting documents must be maintained. Good records make audits less painful and maximize allowable deductions.

For more on estimated payments and forecasting irregular income (seasonal or gig), see our practical guide: Managing Estimated Taxes for Seasonal and Gig Income.

Entity choice and tax planning (brief, practical notes)

Entity choice affects how income is taxed and whether owners pay self-employment tax on all business earnings. For many small businesses:

• Sole proprietors pay income tax and self-employment tax (Social Security and Medicare) on net business income using Schedule SE.
• S corporations can allow owners to take a reasonable salary (subject to payroll taxes) and distribution of remaining profits (which may avoid self-employment tax on the distribution). S-election requires deliberate payroll compliance and documentation.
• Partnerships and LLCs taxed as partnerships flow income through to partners, who pay income and self-employment tax on distributive shares (depending on classification).

Structuring decisions should balance liability protection, administrative cost, and tax efficiency. For a detailed discussion about entity choices and reducing self-employment taxes, see our related article: Using Entity Structures to Reduce Self-Employment Taxes.

Recordkeeping and software tips

• Keep digital records: Scan receipts or use software that attaches receipts to transactions. Many tax-savvy clients use QuickBooks or Xero to tag deductible categories in real time.
• Track mileage: Either use a dedicated app or a written log; the IRS standard mileage rate changes annually and requires contemporaneous logs.
• Reconcile monthly: Match bank and credit card statements to your ledger every month to catch errors early.
• Work with payroll professionals: Payroll providers reduce compliance risk and handle payroll tax deposits, W-2s and 1099s.

Dealing with missed deadlines, audits, and penalties

If you miss a filing deadline: file as soon as possible, pay any tax due, and contact the IRS if you cannot pay immediately—options include payment plans and, in some circumstances, penalty abatement. Penalties accrue for late filing and late payment; interest continues until the balance is paid.

If you receive an IRS notice or audit: respond promptly, provide requested documentation, and consider professional help from a CPA or enrolled agent. Keep copies of everything and use certified mail or secure portal communication when requested documents are sensitive.

Real-world example (anonymized)

A baker operating as a sole proprietor shifted to an S corporation after a year with rising profits. The owner implemented reasonable payroll and began taking distributions. With help from their CPA, they reduced self-employment tax exposure and established a more consistent estimated tax schedule. The change required additional payroll compliance but produced real tax savings over time.

Bottom line: actionable next steps

1. Confirm your entity type and the federal forms it requires.
2. Separate business from personal finances and keep timely records.
3. Know the key deadlines: March 15 (partnerships and S corps), April 15 (individuals and many corporations), and quarterly estimated dates for payments.
4. File extensions if needed, but pay estimated tax by the original deadline.
5. Use accounting software or a bookkeeper and consult a CPA for entity or election decisions.

For compliance-focused filing and recordkeeping steps, consult: Small Business Compliance: Filing, Withholding and Recordkeeping Checklist.

Sources and further reading

• IRS — Small Businesses & Self-Employed: https://www.irs.gov/businesses/small-businesses-self-employed
• IRS estimated taxes: https://www.irs.gov/businesses/small-businesses-self-employed/estimated-taxes
• SBA — Simple Guide to Filing Small Business Taxes: https://www.sba.gov/article/2020/mar/20/simple-guide-filing-small-business-taxes
• IRS forms: 1040, Schedule C; 1065; 1120; 1120-S; 941; 940; 1099-NEC (links available on the IRS website)

Professional disclaimer: This article is educational and reflects common federal filing rules as of 2025. It is not personalized tax advice. Tax rules change and state/local requirements vary—consult a CPA or tax professional for advice tailored to your business and state.