Imagine writing a check to the IRS four times a year and having no idea whether the amount is right, too low, or embarrassingly high. That is the reality for a surprising number of business owners. They pay something because they know they are supposed to. However, they have never actually sat down and figured out whether that number makes sense.
June 15th, 2026 is the Q2 estimated tax deadline. It is coming up faster than most people realize. More importantly, it is a deadline that punishes guessing and rewards preparation in equal measure. So let me walk you through what Q2 estimated taxes actually are, why paying the wrong amount costs you either way, and what smart business owners do before that date arrives.
Q2 Estimated Taxes Explained Without the Jargon
The US tax system runs on a pay-as-you-go model. If you are an employee, your employer withholds taxes from every paycheck and sends that money to the IRS on your behalf. However, if you own a business, nobody withholds anything for you. Therefore, the IRS expects you to send in your own payments throughout the year, broken into four quarterly installments.
Those installments follow a specific schedule. Q1 covers income earned from January through March, with a deadline of April 15th. Q2 covers April and May, with a deadline of June 15th. Q3 covers June through August, due September 15th. Q4 covers September through December, due January 15th of the following year.
Notice something unusual about that Q2 window. It only covers two months instead of three. That quirk catches people off guard every single year. However, the payment calculation is not based on two months of income. It is based on your total estimated annual liability divided across all four installments. More on that in a moment.
Who Actually Needs to Pay Estimated Taxes
Not everyone needs to make quarterly estimated payments. However, if you are a business owner who expects to owe at least $1,000 in federal taxes after subtracting withholding and credits for the year, the IRS generally expects you to pay in quarterly installments under IRC Section 6654.
For S-Corporation owners specifically, the picture is a little more layered. Your S-Corp does not pay federal income tax at the entity level. Instead, your share of the profits passes through to your personal return via the K-1. As a result, you pay taxes on that income personally, which means quarterly estimated payments are your responsibility, not the corporation’s.
However, if you also draw a W-2 salary from your S-Corp, which you should be doing if you have been following along with my earlier piece on reasonable salary requirements, that salary does have withholding. The question becomes whether that withholding is enough to cover your total liability, including the pass-through income. For most S-Corp owners with meaningful profits, it is not. Therefore, estimated payments fill the gap.
The Two Ways Business Owners Get This Wrong
In my experience, business owners make one of two mistakes with quarterly estimated taxes. The first is underpaying. The second, which surprises people, is overpaying. Both have real costs.
Underpaying is the more obvious problem. If you do not pay enough throughout the year, the IRS charges an underpayment penalty under IRC Section 6654. As of 2026, that penalty rate is calculated based on the federal short-term rate plus three percentage points. It does not sound catastrophic, but it compounds across the entire period you were underpaid, and it adds up faster than people expect. The penalty applies even if you pay your full balance by April 15th. The IRS does not care that you eventually paid. It cares that you were late during the year.
Overpaying is the mistake that feels safe but is not. When you send too much to the IRS each quarter, you are essentially giving the government an interest-free loan. That money sits with the IRS earning nothing while you could be using it to pay down debt, invest in your business, or build your reserves. Getting a refund in April is not a win. It means you overfunded the government for twelve months and received zero benefit for doing so.
A tax refund is not free money. It is your own money that the IRS held all year without paying you a cent of interest.
I don’t know about you… but I would rather earn that interest myself. Regardless how small it may be.
The Safe Harbor Rules That Protect You
Here is the good news. The IRS gives you a perfectly legal way to avoid the underpayment penalty without having to predict your income perfectly. It is called the safe harbor rule, and it works like this.
If your estimated payments throughout the year equal at least 100% of your prior year tax liability, you will not owe an underpayment penalty regardless of how much more you actually owe when you file. For example, if your total 2025 federal tax bill was $40,000, then paying $10,000 per quarter in 2026 fully protects you from underpayment penalties, even if your 2026 liability turns out to be significantly higher.
There is one important adjustment for higher earners. If your adjusted gross income exceeded $150,000 in the prior year, the safe harbor threshold increases to 110% of last year’s tax liability rather than 100%. So in that case, if your 2025 tax bill was $40,000, you would need to pay at least $44,000 in total estimated payments during 2026 to stay protected. That works out to $11,000 per quarter.
This is one of the most useful and most overlooked tools in quarterly tax planning. It removes the guesswork entirely. You are not trying to predict the future. You are simply basing your payments on a number you already know.
What Smart Business Owners Do Before June 15th
If you have been building your business seriously this year and your income is tracking higher than last year, safe harbor alone may not be the complete answer. Yes, it protects you from penalties. However, it does not prevent a large tax bill landing in April if your actual income jumped significantly. That is where current-year estimation becomes important.
The most effective approach combines both methods. First, calculate your safe harbor number based on your 2025 return. Second, make a reasonable estimate of your 2026 income through the end of Q2 and compare that to your prior year liability. If your current year appears to be substantially higher, consider voluntarily paying more than the safe harbor minimum to avoid a large April balance due.
For S-Corp owners specifically, the pass-through income conversation is worth having with your advisor now rather than in December. As I have written before in my piece on why your CPA cannot save you in January, the decisions that actually move the needle on your tax bill are made mid-year, not after the year closes. June is exactly that kind of mid-year moment.
I also want to flag something practical for business owners whose income varies month to month. The IRS does allow an annualized income installment method under IRS Form 2210, which lets you calculate each quarterly payment based on your actual income through that period rather than dividing your annual estimate by four. This can be genuinely useful if your business has seasonal patterns or if one quarter was unusually strong or weak. However, the calculation is more complex, and it requires careful documentation to get right.
State Estimated Taxes Deserve Attention Too
Most of the conversation around quarterly taxes focuses on federal obligations, and for good reason. However, if you operate in a state with an income tax, your state likely has its own estimated payment requirements running on a similar schedule.
Take for example Florida and Texas, where many of my clients operate, has no personal state income tax, which is one of the many reasons relocating here makes financial sense for business owners from higher-tax states. However, if you have operations, employees, or nexus in other states, those obligations exist and carry their own penalty structures. Do not assume that getting federal right means you are covered everywhere.
The Practical Steps to Take Right Now
Let me make this as concrete as possible because June 15th is genuinely not far away.
First, pull your 2025 federal tax return and find your total tax liability on line 24 of your Form 1040. That is your baseline safe harbor number. If your AGI was under $150,000, your annual safe harbor target is that number exactly. If your AGI exceeded $150,000, multiply that number by 1.10 to get your 110% safe harbor target.
Second, add up what you already paid for Q1. Subtract that from your annual safe harbor target. Divide the remainder by three to spread it evenly across Q2, Q3, and Q4. That gives you your minimum Q2 payment to stay protected.
Third, take a realistic look at how 2026 is tracking compared to 2025. If revenue is up meaningfully, consider paying more than the minimum. A larger Q2 payment now is far less painful than a surprise balance due next April, and it keeps your cash planning clean throughout the rest of the year.
Finally, make the payment. You can do this directly through the IRS at IRS Direct Pay or through the Electronic Federal Tax Payment System at EFTPS. Both are free, both are secure, and both give you immediate confirmation that your payment was received.
Pulling It All Together
Quarterly estimated taxes are one of those areas where doing the math correctly upfront saves you real money, real penalties, and a genuinely unpleasant conversation with your accountant in April. The June 15th deadline for Q2 is not something to react to at the last minute. It is something to prepare for with a clear number in hand.
Safe harbor protects you from penalties. Smart estimation protects you from surprises. Used together, they give you control over one of the most predictable cash flows in your business, which is ultimately what good tax planning is all about. The business owners who handle this well are not doing anything complicated. They are simply paying attention to the calendar and doing the math before the deadline, not after.
That kind of proactive thinking is exactly what separates a reactive tax filer from a business owner who actually has a strategy.
Welcome to the New Age of Accounting. Let’s begin.
P.S. If you found this article helpful, you’ll love my new book S-Corp Mastery: How Smart Business Owners Maximize Tax Savings & Build a Lasting Legacy. It’s now live and available in a sleek, easy-to-read PDF version. Grab your copy here
Chris is the Managing Partner at Weston Tax Associates, a best-selling author, and a renowned tax strategist. With over 20 years of expertise in tax and corporate finance, he simplifies complex tax concepts into actionable strategies that drive business growth. Originally from Sweden, he now lives in Florida with his wife and two sons.
