Small Business Tax Deadlines: A Complete Calendar Guide

Missing a Tax Deadline Is Expensive

Tax deadlines are one of those things that feel manageable until you miss one. The IRS charges penalties and interest for late filings and late payments, and those costs add up quickly. A failure-to-file penalty can reach up to 25% of the unpaid tax, and failure-to-pay penalties accrue monthly until the balance is resolved.

The challenge for small business owners is that tax deadlines are not just once a year. Depending on your business structure, you may have quarterly estimated tax payments, monthly or semi-weekly payroll tax deposits, annual information returns, and other filings scattered throughout the year.

This guide lays out the key federal tax deadlines every small business owner should know, organized by type. Use it to build your own tax calendar so nothing catches you off guard.

Quarterly Estimated Tax Payments

If your business expects to owe $1,000 or more in federal taxes for the year, you are generally required to make estimated tax payments quarterly rather than waiting until you file your annual return. This applies to sole proprietors, partners, S-corp shareholders, and anyone else who receives income that is not subject to withholding.

When They Are Due

Estimated tax payments follow a consistent annual pattern:

• First quarter: Due in mid-April
• Second quarter: Due in mid-June
• Third quarter: Due in mid-September
• Fourth quarter: Due in mid-January of the following year

The exact dates can shift by a day or two when they fall on weekends or holidays, so check the IRS calendar each year for the precise due dates. The IRS publishes these in Publication 509 (Tax Calendars).

How to Calculate Your Payments

You can base your estimated payments on either your expected current-year tax liability or your previous year's tax liability. The safe harbor rule says you will avoid penalties if you pay at least 100% of the prior year's tax liability through your estimated payments (110% if your adjusted gross income exceeds a certain threshold). Your accountant or tax software can help you determine the right amount.

The Penalty for Underpaying

If you do not pay enough through estimated taxes, the IRS charges an underpayment penalty. The penalty is essentially interest on the amount you should have paid, calculated for each quarter. It is not devastating, but it is money you did not need to spend.

Annual Business Tax Returns

How Deadlines Differ by Entity Type

One of the most confusing aspects of business taxes is that the filing deadline depends on how your business is structured.

Sole Proprietorships and Single-Member LLCs. These file as part of your personal tax return on Schedule C. The deadline is April 15 (or the next business day if it falls on a weekend or holiday). You can request a six-month extension using Form 4868, which pushes the filing deadline to October 15. An extension gives you more time to file but does not extend the time to pay, any taxes owed are still due by the original April deadline.

Partnerships and Multi-Member LLCs. These entities file Form 1065. The deadline is March 15. A six-month extension is available using Form 7004, pushing the deadline to September 15. Partnerships are pass-through entities, meaning the business itself does not pay taxes. Instead, it issues Schedule K-1 forms to each partner, who reports their share of income on their personal return. This is why partnerships file a month earlier, partners need their K-1 information to complete their own returns.

S-Corporations. S-corps also file on March 15 using Form 1120-S, with a six-month extension available to September 15. Like partnerships, S-corps are pass-through entities and issue K-1s to shareholders.

C-Corporations. C-corps file Form 1120. The deadline is April 15 for calendar-year corporations. A six-month extension pushes it to October 15. C-corps pay taxes at the entity level, so there are no K-1s.

Why the March 15 Deadline Matters

If your business is a partnership or S-corp, the March 15 filing deadline is not just about the business return. It is about getting K-1 information to your partners or shareholders in time for them to file their personal returns by April 15. Missing the March 15 deadline can create a chain reaction of delays for everyone involved.

Payroll Tax Deadlines

If you have employees, payroll taxes add a whole separate set of deadlines to your calendar.

Deposit Schedules

The IRS assigns employers either a monthly or semi-weekly deposit schedule for federal income tax withholding, Social Security, and Medicare taxes. Your deposit schedule is determined by the total tax liability you reported during a lookback period.

• Monthly depositors must deposit payroll taxes by the 15th of the following month.
• Semi-weekly depositors must deposit within a few business days of each payday, depending on which day of the week employees are paid.

Getting deposits in on time is critical. The penalties for late payroll tax deposits are steep, ranging from 2% to 15% of the unpaid amount depending on how late the deposit is.

Quarterly Payroll Tax Returns

Most employers file Form 941 (Employer's Quarterly Federal Tax Return) four times a year:

• First quarter: Due April 30
• Second quarter: Due July 31
• Third quarter: Due October 31
• Fourth quarter: Due January 31

Form 941 reconciles the payroll taxes you withheld and deposited during the quarter. Even if you deposited everything on time, you still need to file this form.

Annual Payroll Filings

At the end of each year, employers must also:

• File Form 940 (Federal Unemployment Tax Act return) by January 31.
• Provide W-2 forms to employees by January 31.
• File W-2 copies with the Social Security Administration by January 31.

Information Returns: 1099s

If your business paid independent contractors, freelancers, or certain other non-employees $600 or more during the year, you are required to file 1099 forms.

Key 1099 Deadlines

• 1099-NEC (Nonemployee Compensation). Due to recipients and the IRS by January 31. This is the form used for payments to independent contractors. If January 31 falls on a weekend or federal holiday, the deadline rolls to the next business day (for example, for 2026 filings the deadline was February 2 because January 31, 2026 fell on a Saturday).
• 1099-MISC (Miscellaneous Income). Generally due to recipients by January 31, except amounts in Box 8 (substitute payments in lieu of dividends or interest) and Box 10 (gross proceeds paid to attorneys), where the recipient-copy deadline is February 15. The IRS filing deadline is February 28 on paper, or March 31 if filing electronically. Same weekend/holiday rollover rule applies.

Why 1099 Compliance Matters

The IRS uses 1099 data to cross-reference what recipients report on their own tax returns. If you fail to issue 1099s, you face penalties that increase based on how late you file. More importantly, you may lose the ability to deduct those payments as business expenses if the IRS challenges them.

Sales Tax Deadlines

While this guide focuses on federal taxes, it is worth noting that sales tax deadlines are a major compliance area for many small businesses. Sales tax is administered at the state level, and filing frequencies (monthly, quarterly, or annually) depend on your sales volume and the state's rules. If you collect sales tax in multiple states, each one has its own schedule.

Tips for Staying on Top of Tax Deadlines

Build a Tax Calendar

At the start of each year, map out every tax deadline that applies to your business. Include estimated tax payments, payroll deposits, quarterly filings, annual returns, and information return deadlines. Post it somewhere visible and set digital reminders.

Use a Payroll Service

If you have employees, a reputable payroll service handles tax calculations, withholding, deposits, and quarterly filings for you. This is one of the easiest ways to reduce your payroll tax compliance burden and avoid costly mistakes.

Separate Your Tax Money

A common trap for small business owners is spending money that should be set aside for taxes. Open a separate bank account for tax obligations and transfer estimated amounts into it regularly. When deadlines arrive, the money is already there.

File Extensions if You Need Them, but Pay on Time

Extensions give you more time to file, not more time to pay. If you think you might owe taxes and cannot finish your return on time, file the extension and send a payment with your best estimate of what you owe. This avoids the failure-to-file penalty, which is much steeper than the failure-to-pay penalty.

Stay Current on Changes

Tax rules and deadlines can change. New legislation, IRS guidance, and inflation adjustments can all affect what you owe and when. Bizmoon's compliance monitoring tracks regulatory changes at the federal and state level so you are alerted when something relevant to your business changes, including tax-related regulations.

Learn more about how Bizmoon works or check out our pricing plans.

Start Building Your System

Tax compliance is not optional, and the cost of mistakes is real. But with a solid calendar, the right tools, and a little discipline, you can stay on top of every deadline without it consuming your life.

Create a free Bizmoon account to start monitoring the tax and regulatory changes that affect your small business. Setup takes just a few minutes.