Small Business Taxes: A Complete Beginner's Guide

Taxes are the single largest expense for most small businesses—and the most common source of cash flow crises, IRS notices, and founder burnout. Unlike employees whose taxes are withheld automatically, business owners must calculate, pay, and document their own taxes across multiple categories, often quarterly. A single missed quarterly payment can trigger penalties; a single misclassified expense can trigger an audit.

This guide walks through every tax a small business owner needs to understand, how each is calculated, when each is due, and the strategies that legally minimize what you owe.

The six types of small business taxes

Most small businesses deal with at least four of the following six tax categories. The mix depends on your entity type, location, and industry.

1. Income tax (federal, state, local)
2. Self-employment tax (Social Security and Medicare)
3. Estimated quarterly taxes
4. Payroll taxes (if you have employees)
5. Sales tax (if you sell taxable goods or services)
6. Excise taxes (specific industries only)

1. Income tax: pass-through vs. C-corp

How your business is taxed depends on its legal structure. Most small businesses are pass-through entities—sole proprietorships, partnerships, LLCs, and S-corporations—where business income passes through to the owner's personal tax return. Only C-corporations pay tax at the entity level.

Pass-through entities

For sole proprietors and single-member LLCs, business income is reported on Schedule C of your personal tax return (Form 1040). The net profit flows to your 1040 and is taxed at your personal income tax rates.

For partnerships and multi-member LLCs, the business files an informational return (Form 1065) and issues K-1s to each partner. Each partner reports their share of profit on their personal return.

For S-corporations, the business files Form 1120-S and issues K-1s. The owner must take a "reasonable salary" (subject to payroll taxes) plus distributions (not subject to payroll taxes)—a key tax planning strategy we'll cover below.

QBI deduction (Section 199A)

The 2017 Tax Cuts and Jobs Act created a 20% deduction on Qualified Business Income from pass-through entities. If your business generates $100,000 in QBI, you may deduct $20,000 from your taxable income—effectively reducing the tax rate on business income by 20%.

The deduction has income limits: it begins phasing out at $191,950 (single) or $383,900 (married filing jointly) in 2024, and disappears entirely at $241,950 (single) or $483,900 (MFJ). Above those thresholds, the calculation gets complex—based on W-2 wages paid and unadjusted basis of property. Most small businesses below the income limits simply take the 20% deduction.

C-corporations

C-corps pay a flat 21% federal corporate income tax. Profits distributed as dividends are taxed again on shareholders' personal returns at the qualified dividend rate (0%, 15%, or 20% depending on income). This "double taxation" is the main reason most small businesses avoid C-corp status—unless they're venture-backed startups planning to raise institutional capital.

2. Self-employment tax

Self-employment (SE) tax covers Social Security (12.4%) and Medicare (2.9%) for business owners—totaling 15.3% of net business profit. Employees pay half (7.65%) via withholding and their employer pays the other half. Self-employed individuals pay both halves, but can deduct the employer half (7.65%) from their taxable income.

For 2024, the Social Security portion applies to the first $168,600 of net SE income. Medicare (2.9%) has no cap, and high earners pay an additional 0.9% Medicare surtax above $200,000 (single) or $250,000 (MFJ).

The S-corp tax savings

For businesses with profits above roughly $60,000, electing S-corp status can save thousands in SE tax. As an S-corp owner, you must pay yourself a "reasonable salary" subject to payroll taxes (15.3%). Profits beyond your salary can be taken as distributions, which avoid the 15.3% SE tax entirely.

Example: An LLC earning $150,000 net profit pays $22,950 in SE tax. The same business electing S-corp status, paying the owner $80,000 salary, pays $12,240 in payroll tax on the salary + income tax on the remaining $70,000 distribution (no payroll tax). Savings: roughly $10,700 per year, minus payroll service costs (~$1,200/year).

The S-corp election is one of the most powerful tax strategies for established small businesses. Discuss with a CPA before electing—reasonable salary standards vary by industry and the IRS scrutinizes this aggressively.

3. Estimated quarterly taxes

Because business income isn't subject to withholding, the IRS requires quarterly estimated tax payments. The four quarterly due dates are:

• April 15—for income earned January 1–March 31
• June 15—for income earned April 1–May 31
• September 15—for income earned June 1–August 31
• January 15—for income earned September 1–December 31

Underpayment penalties apply if you owe more than $1,000 at year-end and didn't pay at least 90% of current-year tax or 100% of prior-year tax (110% if AGI over $150,000) via quarterly payments. Use Form 1040-ES to calculate and pay.

Safe harbor strategies

The simplest safe harbor: pay 100% of last year's tax liability (110% if prior-year AGI exceeded $150,000) in equal quarterly installments. This eliminates underpayment penalties even if your income doubles. High-growth businesses should estimate current-year liability to avoid a large April surprise.

4. Payroll taxes

Once you hire employees (or pay yourself a salary as an S-corp), you become responsible for payroll taxes:

• FICA—Social Security 6.2% + Medicare 1.45% on wages (employer portion); employee matches via withholding
• FUTA—Federal unemployment tax, 6% on first $7,000 of wages (effectively 0.6% after state credit)
• SUTA—State unemployment tax, varies widely (0.1%–10%+ depending on state and experience rating)
• State withholding—State income tax withheld from employee wages and remitted to the state

Payroll taxes are deposited on a schedule (monthly or semi-weekly depending on size) and reported quarterly on Form 941 (federal) plus state equivalents. Annual Form 940 reports FUTA. W-2s are issued to employees by January 31.

Payroll tax errors are expensive—penalties pile up quickly. Most small businesses use a payroll service (Gusto, ADP, Paychex) for $40–$100/month per employee. The cost is well worth avoiding IRS notices.

5. Sales tax

Sales tax is collected from customers at the point of sale and remitted to the state. Forty-five states plus Washington D.C. have a sales tax; five (Alaska, Delaware, Montana, New Hampshire, Oregon) do not. Rates and rules vary by state, county, and city—what's taxable in one jurisdiction may be exempt in another.

Nexus and post-Wayfair rules

After the 2018 Supreme Court decision in South Dakota v. Wayfair, states can require out-of-state sellers to collect sales tax if they have "economic nexus"—typically $100,000 in annual sales or 200 separate transactions in the state. If you sell online to customers across multiple states, you may have sales tax obligations in many of them.

Sales tax automation tools (TaxJar, Avalara, Sovos) calculate and file across jurisdictions. For businesses selling in 5+ states, automation is essential.

6. Excise taxes

Excise taxes apply to specific industries and products: alcohol, tobacco, fuel, firearms, air travel, heavy trucks, indoor tanning, and others. If you operate in one of these industries, you'll file Form 720 quarterly. Most service businesses and retailers never encounter excise taxes.

Business deductions: what you can write off

Deductions reduce your taxable business income dollar-for-dollar. Track every legitimate business expense throughout the year—missing deductions is the most common way small businesses overpay.

Common deductible expenses

Home office deduction

If you use part of your home regularly and exclusively for business, you can deduct a percentage of home expenses: rent or mortgage interest, property taxes, utilities, insurance, repairs, and depreciation. The percentage is based on square footage—300 sq ft office in a 2,000 sq ft home = 15% deduction.

The simplified method gives you $5/sq ft up to 300 sq ft ($1,500 max) without tracking actual expenses. The regular method requires more record-keeping but usually yields a bigger deduction.

Section 179 and bonus depreciation

Section 179 lets you immediately expense up to $1.22 million (2024) of equipment purchases in the year bought rather than depreciating over 5–7 years. Eligible items include computers, furniture, machinery, and certain vehicles. Bonus depreciation (currently 60% in 2024, phasing down) allows similar immediate expensing of new and used equipment without the Section 179 limit.

Retirement accounts: the biggest deduction

For self-employed owners, retirement accounts offer the largest single deduction:

• Solo 401(k)—Up to $69,000 in 2024 ($23,000 employee + 25% of compensation employer, max $46,000 employer)
• SEP-IRA—Up to 25% of compensation or $69,000, whichever is less
• Defined benefit plan—Up to $275,000+ for high earners over 50

A 45-year-old consultant earning $300,000 can shelter nearly $80,000 in a solo 401(k) + defined benefit plan, saving $25,000+ in taxes. Talk to a financial advisor about which plan fits your income and goals.

Record-keeping that prevents audits

The IRS requires you to keep records supporting every item on your return for at least 3 years (6 years if you underreported income by 25%+, indefinitely if fraud). Best practices:

• Separate business and personal accounts. Comingling is the #1 audit red flag and the #1 reason business owners can't document deductions.
• Use accounting software. QuickBooks, Xero, or Wave track income and expenses automatically. Bank and credit card feeds eliminate manual entry.
• Save receipts digitally. Photograph or scan every receipt. The IRS accepts digital images.
• Maintain a mileage log. Apps like MileIQ or Stride track business driving automatically. Without a log, the IRS disallows mileage deductions in audits.
• Document business purpose on every meal, travel, and entertainment expense.
• Reconcile monthly. Match accounting to bank statements; catch errors early.

When to hire a CPA

Most businesses benefit from a CPA once revenue exceeds $100,000 or the owner is unsure about deductions, entity structure, or quarterly estimates. CPA costs vary: $500–$1,500 for a simple Schedule C return, $1,500–$4,000 for an S-corp return with payroll, $3,000–$10,000+ for complex multi-entity situations.

A good CPA saves more than they cost through deductions you'd miss, entity optimization, and avoiding penalties. They also represent you in audits—worth the cost alone for many owners.

Common mistakes to avoid

• Mixing personal and business finances. Open a separate business checking account on day one. Every transaction through that account is documented for tax time.
• Missing quarterly estimated payments. Underpayment penalties are 8% annualized on the shortfall. Set calendar reminders for April 15, June 15, September 15, January 15.
• Underpaying yourself as S-corp owner. The IRS requires a "reasonable salary." Setting your salary at $20,000 when comparable positions pay $100,000 is audit bait.
• Forgetting state and local taxes. Many cities have their own business taxes (NYC commercial rent tax, San Francisco payroll expense tax, etc.) in addition to state income tax.
• Not tracking depreciation. Major purchases must be depreciated over time. Skipping depreciation means missing legitimate deductions and complicating future sales.
• Classifying employees as contractors. Misclassification triggers back payroll taxes plus penalties. Use IRS Form SS-8 to determine proper classification.
• Ignoring sales tax obligations. Each state has its own rules. Back sales tax plus penalties can exceed annual revenue for online sellers.
• Going it alone on complex returns. If you have multiple entities, rental properties, or international income, hire a CPA. Self-preparation saves $2,000 and triggers $20,000 in audit adjustments.

Frequently asked questions

What's the difference between an LLC and an S-corp for taxes?

An LLC is a legal structure; an S-corp is a tax election. A single-member LLC is taxed as a sole proprietor by default. An LLC can elect S-corp taxation by filing Form 2553. The S-corp election reduces self-employment tax for owners of profitable LLCs by allowing distributions to skip the 15.3% payroll tax.

How much should I save for taxes as a small business?

A common rule: save 30% of net business income for federal and state taxes. High-income businesses (over $200K profit) may need 35–40%. Move the money to a separate savings account weekly or monthly—don't wait until April to find out you owe $40,000.

Can I deduct home office if I also work elsewhere?

Yes, if the home office is your principal place of business or you use it regularly and exclusively for administrative activities and have no other fixed location for those activities. The "exclusive use" rule is strict—a corner of your dining room doesn't qualify.

Do I need to file quarterly taxes my first year in business?

Yes, if you expect to owe more than $1,000 in taxes for the year. First-year quarterly payments are based on estimated income; the safe harbor of 100% of prior-year tax doesn't apply if you had no prior-year tax liability.

What happens if I can't pay my tax bill?

File on time even if you can't pay—the failure-to-file penalty (5%/month) is ten times worse than failure-to-pay (0.5%/month). Pay what you can, then request an installment agreement with the IRS using Form 9465. Most businesses qualify for payment plans up to 72 months.