Quarterly estimated tax payments are prepayments of federal income tax and self-employment tax that the IRS requires from anyone who expects to owe at least $1,000 for the year after subtracting withholding and credits. For 2026, the federal due dates are April 15, June 15, September 15, and January 15, 2027. Idaho takes a different approach at the state level: individuals are not required to make Idaho estimated payments, while corporations expecting to owe $500 or more must prepay.
If you run a sole proprietorship, farm, construction company, or professional practice in Idaho, this guide walks through who has to pay, how much, when, and how to avoid the underpayment penalty.
Who Has to Make Quarterly Estimated Tax Payments?
You generally must make quarterly estimated tax payments if you expect to owe $1,000 or more in federal tax for the year and your withholding will not cover at least the safe harbor amount. The rule is about how you earn, not how much: income that arrives without tax withheld is what triggers the requirement.
That typically includes:
- Sole proprietors and single-member LLC owners reporting business profit on Schedule C
- Partners and multi-member LLC members receiving a K-1
- S corporation shareholders whose salary withholding does not cover their share of pass-through profit
- Farmers and ranchers, subject to special timing rules covered below
- Landlords, and anyone with significant investment, interest, or capital gain income
- Gig and contract workers paid on a 1099
W-2 employees usually do not need to make estimated payments because withholding handles it. Problems tend to show up in the first year someone leaves a paycheck for self-employment, because there is suddenly no employer withholding and self-employment tax of 15.3 percent applies on top of income tax.
When Are Quarterly Payments Due in 2026?
Federal estimated payments follow an uneven schedule: the “quarters” are not equal three-month periods. For the 2026 tax year, the due dates are:
| Payment | Income period | Due date |
|---|---|---|
| Q1 | January 1 to March 31 | April 15, 2026 |
| Q2 | April 1 to May 31 | June 15, 2026 |
| Q3 | June 1 to August 31 | September 15, 2026 |
| Q4 | September 1 to December 31 | January 15, 2027 |
If a due date falls on a weekend or federal holiday, the deadline moves to the next business day. Note that the second payment covers only two months of income and the fourth covers four, which is why owners who calculate payments from actual quarterly profit are sometimes surprised by the math.
How Much Should Each Payment Be?
The IRS gives you two safe harbor targets, and paying the smaller one protects you from an underpayment penalty. You are safe if your combined withholding and estimated payments equal either 90 percent of the tax you will owe for the current year, or 100 percent of the tax shown on last year’s return. If your adjusted gross income was over $150,000 last year, the prior-year target rises to 110 percent.
For most established businesses, the prior-year safe harbor is the simpler play: take last year’s total tax, apply 100 or 110 percent, subtract expected withholding, and divide the rest into four payments. The 90 percent current-year method makes more sense when income is dropping, since it keeps you from prepaying tax on profit you will not earn.
Remember to include self-employment tax in the estimate, not just income tax. Net self-employment earnings are taxed at 15.3 percent for Social Security and Medicare, and half of that amount is deductible. Skipping this piece is one of the most common reasons first-year owners underpay.
What About Idaho State Estimated Payments?
Idaho does not require individuals to make state estimated tax payments, and it does not charge individuals an underpayment penalty for waiting until the return is filed. That surprises many owners moving in from states with mandatory quarterly systems.
Optional does not mean unwise, though. Idaho taxes pass-through business profit on your personal return, so a strong year can produce a large state balance due the following April. Many of our clients make voluntary Idaho prepayments using Form 51 so the state bill arrives already handled.
Corporations are a different story. An Idaho corporation expecting to owe $500 or more in state tax must make estimated payments using Form 41ES, and underpaying can trigger interest. If your business files as a C corporation, build Idaho estimates into the same calendar as your federal payments.
What Happens If You Skip a Payment?
If you underpay a quarter, the IRS charges an underpayment penalty that works like interest on the shortfall, calculated from each missed due date until the tax is paid. Because the penalty runs quarter by quarter, a big catch-up payment in January does not erase what accrued in the earlier periods.
There is one useful exception: tax withheld from wages is treated as if it were paid evenly through the year, no matter when it actually comes out. Owners who also draw a W-2 salary, including S corporation owners, can raise their withholding late in the year to cover an earlier shortfall. That is a legitimate correction tool, and it is one reason a year-end planning meeting matters. Falling far behind is a different problem, and it compounds quickly; if that has already happened, our guide on what back taxes are and how to resolve them covers the options.
How to Calculate and Pay in Four Steps
A workable quarterly routine looks like this:
- Project the year. Estimate net business profit, other income, and deductions, or start from last year’s return if income is steady.
- Apply the safe harbor. Choose the 90 percent current-year or 100 to 110 percent prior-year target, whichever is lower, and subtract any withholding.
- Divide and schedule. Split the remainder across the remaining due dates and put them on the calendar with reminders a week early.
- Pay electronically. IRS Direct Pay and EFTPS both confirm payments instantly, and Idaho accepts electronic payments through the State Tax Commission.
Clean books make step one dramatically easier. If your profit number is a guess, quarterly estimates will be too, which is a core reason we pair tax projections with client accounting services for owner-operated businesses.
Special Rules for Farmers and Seasonal Businesses
Farmers and ranchers get their own timing rules. If at least two-thirds of your gross income comes from farming or fishing, you can skip the quarterly schedule entirely and either make a single estimated payment by January 15 or simply file and pay in full by March 1.
Other seasonal businesses, such as construction companies with revenue packed into the summer, can use the annualized income installment method. Instead of four equal payments, you calculate each installment from income actually earned to date, which keeps you from prepaying spring tax on money you will not see until fall. It requires Form 2210 at filing time, but for lumpy income it can materially improve cash flow. This is exactly the kind of decision worth running past a CPA rather than guessing; more on that in our article on avoiding small business tax planning mistakes.
Frequently Asked Questions
What happens if I miss a quarterly estimated tax payment?
Pay as soon as you notice rather than waiting for the next due date. The federal underpayment penalty accrues like interest from the missed date, so every week matters. Missing one quarter does not trigger an audit or a separate filing; the penalty is simply reconciled on Form 2210 with your return.
Do I have to make estimated payments in my first year of self-employment?
If you had no tax liability last year, filed a return covering a full 12 months, and were a US citizen or resident all year, you generally owe no underpayment penalty for the current year. Most new owners still benefit from setting aside 25 to 30 percent of net profit so the first April bill is funded.
Does Idaho penalize individuals who skip state estimated payments?
No. Idaho does not require estimated payments from individuals and does not assess an individual underpayment penalty. You will still owe the full state balance at filing, so voluntary prepayments on Form 51 remain a smart cash-management habit for profitable years.
Can I just make one big payment in January instead of four?
For most taxpayers, no. The federal penalty is calculated per quarter, so a January catch-up leaves the earlier shortfalls penalized. The exceptions are qualifying farmers and fishermen, and anyone whose safe harbor is fully covered by wage withholding.
How much should I set aside from each payment I receive?
A common working rule for Idaho self-employed owners is 25 to 30 percent of net profit for combined federal income tax, self-employment tax, and Idaho state tax. Your actual number depends on your bracket, deductions, and entity structure, which is worth confirming with a projection rather than a rule of thumb.
Get Ahead of the September 15 Deadline
The third quarter federal payment for 2026 is due September 15, which makes late summer the right time to check your year-to-date profit against what you have paid in. A mid-year projection can catch an underpayment while there is still time to fix it cheaply. The tax team at Cooper Norman builds quarterly estimate schedules, runs mid-year projections, and handles the calculations behind our tax services for businesses across Idaho. Contact us to put your estimates on autopilot before the next due date.