2026 Small Business Tax Calendar Key Deadlines You Can’t Miss

Starting a new year is exciting, but for many small business owners, January also brings a bit of “tax anxiety.” At BASC Expertise, we combine engineering precision with tax strategy to take that weight off your shoulders.

If you want to avoid IRS penalties and keep your cash flow predictable, you need to mark these dates on your 2026 calendar. Here is your essential guide to staying compliant this year.

January 15, 2026 – Final 2025 Estimated Tax Payment

If you are self-employed or a small business owner, today is the deadline to pay your final quarterly estimated tax payment for the 2025 tax year. Keeping up with these prevents a large, unexpected bill (and interest charges) when you file your final return.

January 31, 2026 – 1099 and W-2 Deadline

This is a major milestone for business owners. By the end of today, you must:

Mail W-2s to your employees.
Send 1099-NEC forms to any independent contractors you paid $600 or more in 2025.
File Copy A of Form 1099-NEC with the IRS.

SEO Tip: Missing the 1099 deadline is one of the most common ways small businesses trigger IRS notices. Get these out early!

March 16, 2026 – S-Corp and Partnership Tax Returns

If your business is an S-Corp (Form 1120-S) or a Multi-Member LLC/Partnership (Form 1065), your tax day comes earlier than the traditional April 15th.

Action Item: Even if you aren’t ready to file, you must file an extension by this date to avoid late-filing penalties.

April 15, 2026 – Individual Income Tax & C-Corp Deadline

The “Big Day” for most taxpayers. This is the deadline for:

C-Corporations (Form 1120).
Sole Proprietors and Single-Member LLCs (filed via Form 1040).
First Quarter 2026 Estimated Tax Payments.

How to Stay Ahead in 2026

Tax season doesn’t have to be a race against the clock. At BASC Expertise, we help our clients move from “reactive” to “proactive.” Whether you are looking for monthly bookkeeping to keep your data clean or a deep-dive tax strategy, we ensure your business runs with the precision of a well-oiled machine.

Not sure which forms you need to file? Don’t guess with your business finances. Check out our Bookkeeping Services to see how we can handle the heavy lifting for you.