Federal income tax is generally paid as income is earned. Employees usually do that through withholding from their paychecks. People with income that is not fully covered by withholding may need estimated payments instead. This includes sole proprietors, independent contractors, partners, S corporation shareholders, landlords, investors with capital gains, retirees, and employees with significant side income.

Estimated payments may cover more than regular income tax. They can also cover self-employment tax, alternative minimum tax, net investment income tax, and other amounts expected on your return. This is why a profitable business owner can have an estimated-tax obligation even when the business itself doesn't have to pay federal income tax at the entity level.

For most individual taxpayers, the IRS rule has three parts. You can avoid estimated payment penalties for 2026 when:

Example: If 2025 AGI was $180,000 and total tax shown on the 2025 return was $20,000, the prior-year safe-harbor amount for 2026 would be:

$20,000×110%=$22,000 

That generally means four payments of $5,500, adjusted for federal withholding and other applicable payments.

The second test is where many people find a safe harbor. If enough tax will be paid through withholding and credits to reach the applicable prior-year or current-year target, separate estimated payments may not be required, even if a balance remains when the return is filed. Avoiding an underpayment penalty and paying the entire final tax bill are not always the same thing.

The required annual amount is generally the smaller of the applicable current-year and prior-year amounts. The safe harbor can prevent an estimated-tax penalty, but it does not erase additional tax created by a more profitable year. A taxpayer who meets the prior-year safe harbor can still owe a sizable amount at filing.

You may not need separate estimated payments when withholding and refundable credits are already sufficient, when the expected balance due is under $1,000, or when you meet a safe harbor. A wage earner with side-business income can often increase Form W-4 withholding instead of sending separate estimated payments. As you can see the tax is still being prepaid, just by a different payment method.

There is also a clean prior-year exception. You do not have to pay estimated tax for 2026 if you had no tax liability for 2025, if you were a U.S. citizen or resident alien for all of 2025 and you had no tax liability for the full 12-month 2025 tax year.  Having received a refund does not necessarily mean you had no tax liability. A refund may simply mean that your payments exceeded your tax.

Suppose a married business owner expects a total 2026 tax of $20,000 and expects $4,000 of withholding. The 90% current-year target is $18,000. If the tax shown on the full-year 2025 return was $12,000 and the higher-income rule does not apply, the prior-year safe harbor is $12,000. The smaller annual target is therefore $12,000. After the $4,000 of expected withholding, the owner would generally need two more $4,000 payments equaling $8,000 of timely estimated payments to reach the $12,000 safe harbor.

That does not mean the remaining projected $8,000 disappears. It may still be due with the return. The safe harbor is mainly a penalty-management rule, not a discount on the tax bill.

Timing Matters Just as Much as the Annual Total

The IRS calculates an underpayment penalty by payment period. Paying the right annual amount late may not repair an earlier underpayment. For calendar-year individuals, the 2026 due dates are April 15, June 15, and September 15, 2026, followed by January 15, 2027. Notice that the schedule is not four equal three-month quarters.

If income arrives unevenly, perhaps from a large year-end project, a seasonal business, or a late investment sale, the annualized income installment method may match payments to when the income was earned. It can reduce or avoid a penalty that would result from pretending the income was earned evenly all year, but using it generally requires Form 2210 and Schedule AI with the return.

Do not wait for a perfect set of books. Start with year-to-date profit, expected income for the rest of the year, projected deductions, self-employment tax, credits, and withholding. Compare the expected payments with both the current-year and prior-year safe-harbor amounts. Revisit the projection when profit, payroll, investments, or major deductions change.

If you or your spouse receives wages or certain retirement distributions, increasing withholding may be simpler than making separate payments. Withholding is generally treated as paid evenly throughout the year for estimated-tax purposes, which can sometimes help address an earlier shortfall. The best choice depends on timing, cash flow, and the facts of the return.

You do not automatically have to make estimated payments just because you own a business, receive a Form 1099, or owed tax last year. You generally need to compare the expected balance due with the $1,000 threshold and then test your projected withholding and credits against the applicable safe harbor. If the numbers show a shortfall, act before the next payment date rather than waiting until the return is prepared.

Estimated taxes become much less intimidating when they are treated as a planning exercise instead of a filing-season emergency. A straightforward projection, updated when circumstances change, can protect cash flow, reduce penalties, and give you a clearer picture of what the year is really producing.

If you are unsure whether your withholding and estimated payments are on track, The Smith Advisory can help you review the numbers and identify the payment target that fits your situation. Feel free to contact us at [email protected] so you can make informed payments now and reduce the chance of an avoidable surprise later.

This article is for general educational and informational purposes only and is not tax, legal, accounting, or financial advice. Tax rules depend on individual facts and may change, and state estimated-tax requirements can differ from federal rules. Consult a qualified tax professional about your circumstances before making or changing a payment strategy.