Tax Tip Tuesday: Estimated Taxes for Business Owners — Why You Can't Afford to Skip Them

If you own a business — whether you're a sole proprietor, a partner, or an S-corp shareholder — you already know the IRS doesn't wait until April to get paid. Our tax system runs on a "pay-as-you-go" model, and for business owners, that usually means quarterly estimated tax payments. Skip them, and you're not just risking a bigger bill next spring; you're signing up for an underpayment penalty on top of it.

This week's Tax Tip Tuesday breaks down why estimated taxes exist, why we bring this up with almost every business-owner client, and closes with a quick self-check quiz so you can see where you stand right now.

Why Estimated Taxes Exist in the First Place

When you're a W-2 employee, your employer withholds tax from every paycheck and sends it to the IRS on your behalf. As a business owner, there's no employer doing that for you — so the IRS requires you to make your own withholding, in the form of quarterly estimated payments, on income like:

• Self-employment / Schedule C net profit

• Partnership and S-corp K-1 income allocated to you

• Rental income or other income without withholding

• Capital gains and investment income above your safe harbor cushion

If you don't pay in enough throughout the year, the IRS charges an underpayment penalty (essentially interest, recalculated quarterly based on current rates) — even if you pay your full balance by the April deadline.

Why I Keep Bringing This Up

I emphasize estimated taxes with almost every business-owner client, every quarter, for three reasons:

1. It protects your cash flow. A surprise five-figure tax bill in April is a lot harder to absorb than four smaller payments spread across the year. Quarterly payments turn a shock into a budget line item.

   
   

2. It catches problems early. When we calculate your estimate each quarter, we're also checking in on how the business is actually performing. That's a built-in planning checkpoint — often the moment we spot an opportunity for a retirement plan contribution, an entity structure question, or a deduction you'd otherwise miss.

   
   

3. It's cheaper to be proactive than reactive. The penalty accrues quarter by quarter. The longer you wait to true up, the more it costs. Paying in on time — or adjusting mid-year when income changes — is almost always cheaper than catching up later.

In short: estimated taxes aren't just a compliance requirement. They're one of the simplest tools we have to keep you ahead of your tax liability instead of chasing it.

The Safe Harbor Rules (How Much Is "Enough")

You generally avoid the underpayment penalty if, through withholding and timely estimated payments, you pay in the smaller of:

• 90% of the tax you'll owe for the current year, or

• 100% of the tax shown on your prior year return (110% if your prior-year AGI was over $150,000, or $75,000 if married filing separately)

The prior-year safe harbor is often the easiest to plan around, especially when income is hard to predict.

2026 Quarterly Due Dates

Payment Period	2026 Due Date
January 1 – March 31	April 15, 2026
April 1 – May 31	June 15, 2026
June 1 – August 31	September 15, 2026
September 1 – December 31	January 15, 2027

What To Do If You're Behind

If the quiz below tells you what you suspected, don't wait for the next deadline to fix it. Depending on where you are in the year, we can often:

• Run a current-year projection to right-size your remaining payments

• Use the prior-year safe harbor to simplify the calculation

• Adjust W-2 withholding (yours or a spouse's) to cover the gap without a separate quarterly payment

• Layer in retirement plan or entity-structure planning while we're already looking at the numbers

Estimated taxes aren't just an IRS formality — they're a planning tool. Paying in quarterly keeps your cash flow predictable, keeps penalties off the table, and gives us a natural checkpoint to catch planning opportunities before the year closes out.

Ready to get your estimated payments dialed in? Email us at info@mkhstaxgroup.com and we'll run your numbers.