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Quarterly Estimated Tax Calculator
What to send the IRS each quarter — and the safe harbour that often makes it a good deal less than a straight quarter of your projected tax.
If nothing is being withheld on your income, the tax is still due through the year rather than all at once in April. It is paid in four instalments, and missing them adds penalties rather than simply deferring the bill.
The part worth knowing is that you rarely have to pay the whole projected amount. There is a safe harbour based on last year’s tax, and where last year was the smaller year, paying against that figure is enough to avoid a penalty even if this year turns out much larger.
This year, as you expect it
Income minus expenses for the whole year. A best estimate is fine — revise it as the year goes on.
From a job, if you have one alongside the business.
Interest, rents, retirement income — anything ordinary that is not wages or business profit.
Each one reduces the projected tax by up to $2,200.
From wages or a pension. This counts toward the same bill, so it reduces what you need to pay in.
What you have sent the IRS toward this year so far.
Last year’s return
The total tax line, not the balance you paid in April. This is what unlocks the prior-year safe harbour.
Above $150,000, the prior-year safe harbour rises from 100% to 110%.
What to pay, and when
Social Security and Medicare on the business profit — the part nobody is withholding for you.
You do not have to pay all of it in instalments. The penalty is avoided by paying the lower of 90% of this year’s tax and 100% of last year’s. Put last year’s total tax in and this will use whichever is lower.
90% of this year’s projected tax. No prior-year figure entered.
Withholding and payments you have already made.
$13,966 to pay across four instalments. If part of the year has already gone, catch up on the next one rather than spreading the shortfall — the penalty is worked out period by period.
Due dates for 2026
1st instalment — April 15, 2026
2nd instalment — June 15, 2026
3rd instalment — September 15, 2026
4th instalment — January 15, 2027
They are not quarter-ends. The second falls in June, not July, which is the one people miss.
2026 federal rates and brackets. State estimated payments are separate and not included.
What this does not include
This projects a federal instalment from figures you expect rather than figures that have happened, so it is only as good as the estimate you put in. Revise it when the year does something you did not plan for.
- South Carolina estimated payments. The state has its own instalments and its own dates. They are not in this figure.
- The annualised income method. Where income arrives unevenly — a seasonal trade, one large job — instalments can be matched to when it was actually earned instead of being split into four equal parts. That usually reduces the earlier payments and is worth asking about.
- The Earned Income Tax Credit, and credits for education, energy and childcare. Any of them can reduce what you need to pay in.
- The QBI deduction, which can be substantial on business profit and is not modelled here.
- Increasing withholding instead. If you also have a job, covering the business liability through your W-4 is often simpler than four separate payments — and tax withheld counts as paid evenly across the year however late in it you withhold it. See the withholding calculator.
This is an estimate, not a tax return. It is a projection from the figures you entered, using published federal rates for the tax year shown. It is not a completed or filed return, it is not professional tax advice, and it does not create a client relationship. Your actual liability depends on your full circumstances and on documents this page never sees. Before acting on a number here — changing your withholding, setting an estimated payment, spending a refund — have it checked against your real situation. Call (864) 781-4035 or book a free consultation.
The safe harbour, and why it matters
A penalty is avoided by paying, across the year, the lower of two figures: 90% of what you end up owing for this year, or 100% of what you owed last year. Where last year’s adjusted gross income was over $150,000, that second figure becomes 110%.
That is a genuinely useful rule for anyone whose income moves. A business having its best year can pay instalments based on a much smaller previous year, keep the difference working in the business, and settle the balance at filing without a penalty. It is not a way of avoiding the tax — the balance is still due in April — but it is a way of not overpaying all year.
The catch is that it needs last year’s total tax figure, from the return itself rather than from the cheque you wrote. Put it in the last two fields and the calculator will use whichever route is cheaper.
The dates are not quarter-ends
The instalments fall in April, June, September and the following January. The second one is two months after the first, not three, and it is the one people miss almost every year because they assume it lands in July.
A late instalment is charged from its own due date, so the penalty is worked out period by period rather than on the year as a whole. That means catching up on the next instalment rather than spreading a shortfall across the remaining ones.
When uneven income changes the answer
The four-equal-instalments approach assumes income arrives steadily. Plenty of businesses do not work that way — a seasonal trade, a single large contract, a year where everything lands in the autumn.
There is a method that matches instalments to when income was actually earned, which generally reduces the earlier payments substantially. It requires more record-keeping and it is not modelled here, but if your income is genuinely lumpy it is worth asking about rather than paying four equal amounts against money you had not yet earned.
Quarterly payment questions
What happens if I just skip them and pay in April?
The tax is the same, but an underpayment penalty is added, calculated from each missed due date. It is charged like interest rather than as a flat fine, so a small shortfall costs little and a whole year of skipped instalments costs a good deal more.
Can I use my W-4 instead of making payments?
If you also have a job, often yes, and it is usually simpler. Tax withheld from wages counts as paid evenly across the year regardless of when it was withheld, which makes it a better tool for catching up late in the year than a payment is. See the withholding calculator.
Do I need to pay South Carolina estimates too?
Usually, if you owe state tax and nothing is being withheld. South Carolina has its own instalments and its own dates, and this calculator is federal only. We set both up together as part of tax planning.
My income is nothing like last year. Which figure do I use?
The calculator picks the lower of the two safe harbours for you. If this year is much bigger, last year’s figure will usually be the cheaper route — but remember the balance is still due at filing, so put the difference aside rather than spending it.
It is already mid-year and I have paid nothing. What now?
Catch up on the next instalment rather than spreading the shortfall, because the penalty runs from each date separately. If you have a job as well, raising your withholding can retroactively fix earlier periods in a way that a payment cannot. It is worth a short conversation — call (864) 781-4035.
Not the question you had? The full tax FAQ covers more ground, and our client reviews say what the work is actually like.
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