Small Business Taxes 101: Deadlines, Estimated Payments and Deductions

Taxes are the one business expense nobody can skip, and the one most new owners understand least. This guide walks through which taxes a small business owes, when they are due, how quarterly estimated payments work and how to set up a simple system so tax season stops being a crisis.

When you were an employee, tax mostly happened to you. Your employer withheld it, filed the forms and sent you a summary once a year. As a business owner, you are now the employer, the accountant and the taxpayer at the same time, and the system assumes you know the rules.

The good news is that the rules for a typical small business are not that complicated once you see the structure. This guide uses US federal taxes as the main example because that is where most of our readers are, but the same categories exist almost everywhere. Where your country differs, the principles still apply: know which taxes you owe, know when they are due and keep enough cash aside to pay them.

The four taxes most small businesses pay

Before deadlines and forms, get clear on what you are actually paying for. Most small businesses deal with some mix of these four.

1. Income tax on business profit

You pay income tax on profit, which is revenue minus deductible expenses, not on revenue itself. How you pay it depends on your legal structure. In the US, a sole proprietorship or single-member LLC reports profit on Schedule C of the owner's personal return. Partnerships and S corporations file an information return and pass profit through to the owners, who pay tax personally. A C corporation pays its own corporate income tax, currently a flat 21% at the federal level, and owners pay tax again on dividends.

Many US states also charge income tax, and a handful charge a franchise or gross receipts tax on businesses instead of or in addition to it. Outside the US, the split between personal and corporate tax works differently in every country, so check the local rules for your entity type.

2. Self-employment tax or payroll tax

This is the one that surprises first-year owners. In the US, employees and employers each pay 7.65% of wages toward Social Security and Medicare. When you work for yourself, you pay both halves, a combined 15.3% self-employment tax on net earnings. The Social Security portion (12.4%) only applies up to an annual wage base that the Social Security Administration adjusts each year, while the Medicare portion (2.9%) applies to all earnings. You can deduct half of your self-employment tax when calculating your income tax, which softens the blow slightly.

If you have employees, you also withhold their income tax and their share of Social Security and Medicare, add the employer share, and send it all to the IRS on a monthly or semi-weekly schedule, plus federal and state unemployment tax.

3. Sales tax, VAT or GST

If you sell taxable goods or services, you collect tax from customers and pass it on to the government. In the US this is sales tax, set by states and local jurisdictions. In most other countries it is VAT or GST. Either way, this money is never yours. It belongs to the tax authority from the moment you collect it, which is why mixing it with operating cash is so dangerous.

4. Local business taxes and fees

Cities and counties often charge business license fees, personal property tax on equipment, or a local gross receipts tax. These are usually small, but missing them leads to penalties and, in some places, a suspended license.

How estimated tax payments work

The US tax system is pay-as-you-go. Employees meet this requirement through withholding. Business owners meet it through quarterly estimated payments. The IRS generally expects you to make estimated payments if you will owe $1,000 or more in tax for the year after subtracting withholding and credits (the threshold for corporations is $500).

Notice that the "quarters" are not equal. The second period is only two months long and the third is three, while the fourth stretches to four. When a due date falls on a weekend or holiday, it moves to the next business day. Individuals use Form 1040-ES to calculate and pay; corporations use Form 1120-W as a worksheet and pay electronically.

The safe harbor rule

You do not have to predict your profit perfectly. The IRS waives the underpayment penalty if your payments during the year total at least 90% of the current year's tax, or 100% of last year's tax (110% if your adjusted gross income was above $150,000). This is called the safe harbor. For a business with uneven income, paying based on last year's return is the simplest way to stay penalty-free, then settling any difference in April.

Key filing deadlines by business type

Filing a return and paying tax are two separate deadlines, and they do not always match. These are the federal dates for calendar-year businesses in the US. Fiscal-year businesses and businesses in other countries have different dates, and the IRS sometimes extends deadlines after disasters, so confirm the current year's calendar.

• Sole proprietors and single-member LLCs: Schedule C is filed with your Form 1040, due April 15. An extension to October 15 is available, but it extends the time to file, not the time to pay.
• Partnerships and multi-member LLCs: Form 1065 is due March 15, a month earlier, so partners receive their Schedule K-1 in time for their personal returns.
• S corporations: Form 1120-S is also due March 15, with K-1s to shareholders.
• C corporations: Form 1120 is due April 15 for calendar-year companies.
• Employers: W-2s to employees and 1099-NEC forms to contractors are due by January 31. Quarterly payroll returns (Form 941) are due at the end of the month following each quarter.

Deductions: the basics every owner should know

A deduction is an ordinary and necessary business expense that reduces taxable profit. The IRS uses exactly those two words: "ordinary" meaning common in your trade, and "necessary" meaning helpful and appropriate. The main categories most small businesses use are:

• Cost of goods sold, including inventory and materials
• Rent, utilities and a home office if you qualify
• Wages, contractor payments and employee benefits
• Software, subscriptions, supplies and advertising
• Vehicle use for business, by mileage or actual cost
• Business insurance, professional fees and bank charges
• Depreciation on equipment, or an immediate write-off under Section 179 up to an annual limit

Pass-through business owners may also qualify for the qualified business income deduction, which can shave up to 20% off qualified profit, subject to income limits and rules about the type of business. We cover deductions in detail, including how to document each one, in a separate article on common small business tax deductions.

How to set up a tax system that runs itself

1. Open a separate tax savings account. Every time a customer pays you, move a fixed percentage into it. For a US sole proprietor with moderate income, 25% to 30% of profit is a common starting point; owners in high-tax states or with higher incomes may need more. Adjust after your first return.
2. Put every deadline on a calendar with reminders. Add the four estimated payment dates, your filing date, payroll deposit dates and sales tax due dates. Set reminders a week ahead.
3. Choose bookkeeping software and keep it current. Weekly categorizing takes ten minutes. Yearly categorizing takes a weekend and produces worse results.
4. Pay estimates from last year's numbers. Use the safe harbor as your floor. If the year is going much better, increase the later payments.
5. Review your structure once a year. As profit grows, an S corporation election or other structure may reduce self-employment tax. Run the numbers with an accountant rather than guessing.
6. Book a tax professional before December. A one-hour planning call in the fourth quarter can still change what you owe. A call in April cannot.

Penalties and what happens if you miss a deadline

The IRS charges separate penalties for filing late and for paying late, plus interest on unpaid balances. The failure-to-file penalty is generally far larger than the failure-to-pay penalty, which leads to one simple rule: always file on time, even if you cannot pay the full amount. You can request an installment agreement for the balance. Payroll tax deposits carry their own penalties and are treated more seriously than most other taxes, because the money was withheld from employees.

If you are outside the United States

The categories above translate well, but the details do not. Many countries require VAT or GST registration above a turnover threshold, pay-as-you-go instalments for income tax on a different schedule, and separate filings for corporate and personal tax. Deadlines, rates and thresholds change frequently in every country, so treat the specific figures here as US examples and confirm current rules with your national tax authority or a local accountant.

Frequently asked questions

The bottom line

Small business taxes are a system, not a surprise. Know which of the four taxes apply to you, pay income tax in quarterly estimates using the safe harbor, keep collected sales tax and payroll withholding untouched, and record expenses as they happen. Do that and tax season becomes a routine filing rather than a cash crisis. Rates, thresholds and dates move every year and differ by country, so check the current figures before relying on any number in this guide.