IRS Publication 17 — Your Federal Income Tax (Individuals)

2025 joint return and 2026 separate returns. If you plan to file a separate return for 2026 but you filed a joint return for 2025, your 2025 tax is your share of the tax on the joint return. You file a separate return if you file as single, head of household, or married filing separately. T o figure your share of the tax on the joint return, first figure the tax both you and your spouse would have paid had you filed separate returns for 2025 using the same filing status as for 2026. Then, multiply the tax on the joint return by the following fraction. The tax you would have paid had you filed a separate return The total tax you and your spouse would have paid had you filed separate returns Example. Owen and Sophia filed a joint return for 2025 showing taxable income of $48,500 and tax of $5,346. Of the $48,500 taxable income, $40,100 was Owen’s and the rest was Sophia’s. For 2026, they plan to file married filing separately. Owen figures tax on the 2025 joint return as follows.

Tax on $40,100 based on a separate return … $4,577 Tax on $8,400 based on a separate return … 843 Total … $5,420 Owen’s percentage of total ($4,577 ÷ $5,420) … 84.4465% Owen’s share of tax on joint return ($5,346 × 84.4465%) … $4,514 How To Figure Estimated Tax T o figure your estimated tax, you must figure your expected adjusted gross income (AGI), taxable income, taxes, deductions, and credits for the year.

When figuring your 2026 estimated tax, it may be helpful to use your income, deductions, and credits for 2025 as a starting point. Use your 2025 federal tax return as a guide. You can use Form 1040 -ES and Pub. 505 to figure your estimated tax. Nonresident aliens use Form 1040-ES (NR) and Pub. 505 to figure estimated tax (see chapter 8 of Pub. 519 for more information). You must make adjustments both for changes in your own situation and for recent changes in the tax law. For a discussion of these changes, go to IRS.gov.

For more complete information on how to figure your estimated tax for 2026, see chapter 2 of Pub. 505. When To Pay Estimated Tax For estimated tax purposes, the tax year is divided into four payment periods. Each period has a specific payment due date. If you don’t pay enough tax by the due date of each payment period, you may be charged a penalty even if you are due a refund when you file your income tax return. The payment periods and due dates for estimated tax payments are shown next. For the period: Due date:* Jan. 1–March 31 … April 15 April 1–May 31 … June 15 June 1–August 31 … Sept. 15 Sept. 1–Dec. 31 … Jan. 15, next year . * See Saturday, Sunday, holiday rule and January payment.

Saturday, Sunday, holiday rule. If the due date for an estimated tax payment falls on a Saturday, Sunday, or legal holiday, the payment will be on time if you make it on the next day that isn’t a Saturday, Sunday, or legal holiday. January payment. If you file your 2026 Form 1040 or 1040-SR by February 1, 2027, and pay the rest of the tax you owe, you don’t need to make the payment due on January 15, 2027.

Fiscal-year taxpayers. If your tax year doesn’t start on January 1, see the Form 1040 -ES instructions for your payment due dates. When To Start You don’t have to make estimated tax payments until you have income on which you will owe income tax. If you have income subject to estimated tax during the first payment period, you must make your first payment by the due date for the first payment period. You can pay all your estimated tax at that time, or you can pay it in installments. If you choose to pay in installments, make your first payment by the due date for the first payment period. Make your remaining installment payments by the due dates for the later periods.

No income subject to estimated tax during first period. If you don’t have income subject to estimated tax until a later payment period, you must make your first payment by the due date for that period. You can pay your entire estimated tax by the due date for that period or you can pay it in installments by the due date for that period and the due dates for the remaining periods.

General Due Dates for Estimated Tax Installment Payments Table 4-1.

If you first have income on which you must pay estimated tax: Make installments by:* Make later installments by:* Before April 1 April 15 June 15 Sept. 15 Jan. 15, next year April 1–May 31 June 15 Sept. 15 Jan. 15, next year June 1–Aug. 31 Sept. 15 Jan. 15, next year After Aug. 31 Jan. 15, next year (None) * See Saturday, Sunday, holiday rule and January payment.

How much to pay to avoid a penalty. T o determine how much you should pay by each payment due date, see How T o Figure Each Payment next. How To Figure Each Payment You should pay enough estimated tax by the due date of each payment period to avoid a penalty for that period. You can figure your required payment for each period by using either the regular installment method or the annualized income installment method. These methods are described in chapter 2 of Pub. 505. If you don’t pay enough during each payment period, you may be charged a penalty even if you are due a refund when you file your tax return. If the earlier discussion under No income subject to estimated tax during first period or the later discussion under Change in estimated tax applies to you, you may benefit from reading Annualized Income Installment Method in chapter 2 of Pub. 505 for information on how to avoid a penalty.

Underpayment penalty. Under the regular installment method, if your estimated tax payment for any period is less than one-fourth of your estimated tax, you may be charged a penalty for underpayment of estimated tax for that period when you file your tax return. Under the annualized income installment method, your estimated tax payments vary with your income, but the amount required must be paid each period. See Instructions for Form 2210 for more information. Change in estimated tax. After you make an estimated tax payment, changes in your income, adjustments, deductions, or credits may make it necessary for you to refigure your estimated tax. Pay the unpaid balance of your amended estimated tax by the next payment due date after the change or in installments by that date and the due dates for the remaining payment periods. 42 Chapter 4 Tax Withholding and Estimated Tax Publication 17 (2025)