With tax reform bringing major changes for the current tax year, the Internal Revenue Service today reminded small businesses, self-employed individuals, retirees, investors and others who need to pay their taxes quarterly that the third estimated tax payment for 2018 is due on Monday, Sept. 17, 2018. The fourth and final payment for 2018 is due January 15th.

The Tax Cuts and Jobs Act, enacted in December 2017, changed the way tax is calculated for most taxpayers, including those with substantial income not subject to withholding. Among other reforms, the new law changed the tax rates and brackets, revised business expense deductions, increased the standard deduction, removed personal exemptions, increased the child tax credit and limited or discontinued certain deductions. As a result, many taxpayers may need to raise or lower the amount of tax they pay each quarter through the estimated tax system.

Form 1040-ES, available on IRS.gov, is designed to help taxpayers figure these payments simply and accurately. The estimated tax package includes a quick rundown of key tax changes, income tax rate schedules for 2018 and a useful worksheet for figuring the right amount to pay. The IRS also mailed 1 million Form 1040-ES vouchers with instructions in late March to taxpayers who used this form last year.

A companion publication, Publication 505, Tax Withholding and Estimated Tax, has additional details, including worksheets and examples, which can help taxpayers determine whether they should pay estimated tax, such as those who have dividend or capital gains income, owe alternative minimum tax or have other special situations.

Who needs to pay quarterly?

Most often, self-employed people, including some individuals involved in the sharing economy, need to pay quarterly installments of estimated tax. Similarly, investors, retirees and others – a substantial portion of whose income is not subject to withholding – often need to make these payments as well. Other income generally not subject to withholding includes interest, dividends, capital gains, alimony and rental income.

Because the U.S. tax system operates on a pay-as-you-go basis, taxpayers are required, by law, to pay most of their tax liability during the year. For 2018, this means that an estimated tax penalty will normally apply to any party that pays too little tax — generally less than 90 percent of the tax shown on the return for the current tax year or 100 percent of the tax shown on the return for the preceding tax year — during the year through withholding, estimated tax payments or a combination of the two.

You may avoid a penalty for underpayment of estimated taxes if you owe less than $1,000 in tax after subtracting your withholding and estimated tax payments and credits or if you did not have any tax liability for the preceding taxable year (subject to certain conditions).

Employees have a choice

Many employees who also receive income from other sources may be able to forgo making estimated tax payments and instead increase the amount of income tax withheld from their pay. They can do this by claiming fewer withholding allowances on their Form W-4, based on completing the Deductions, Adjustments, and Additional Income Worksheet in the instructions section. If that’s not sufficient, on the Form W-4 they can ask their employer to withhold an additional flat-dollar amount each pay period.

How and when to pay

For tax-year 2018, estimated tax payment due dates are April 18, June 15, Sept. 17 and Jan. 15, 2019. Taxpayers still due a refund on their 2017 federal income tax return may be able to reduce or even skip one or more of these payments by choosing to apply their 2017 refund to their 2018 estimated tax. See Form 1040 and its instructions for more information.

The fastest and easiest way to make estimated tax payments is to do so electronically using IRS Direct Pay or the Treasury Department’s Electronic Federal Tax Payment System (EFTPS). For information on other payment options, visit IRS.gov/payments. For filers paying by check, the check must be made payable to the “United States Treasury.”

More information about tax withholding and estimated tax can be found on the agency’s Pay As You Go web page as well as in Publication 505, Tax Withholding and Estimated Tax.