Annualized Income Installment Method Definition, When to Use It

What Is the Annualized Income Installment Method?

Taxpayers who are self-employed typically pay quarterly installments of their estimated tax in four even amounts as figured by the regular installment method. Additionally, taxpayers should pay estimated taxes if they receive substantial dividends, interest, alimony, or other forms of income that are not subject to income tax withholding.

When a taxpayer has a fluctuating income, it often causes them to underpay on one or more of the quarterly estimates leading to underpayment penalties. The annualized income installment method calculates the taxpayer’s estimated tax installment payments and helps to decrease underpayment and corresponding underpayment penalties related to fluctuating income. Through the use of the annualized income installment method, taxpayers may estimate their taxes based on known information from the beginning of the tax year through the end of the period paid.

How the Annualized Income Installment Method Works

The purpose of the regular installment method is to figure in quarterly tax installments. It divides the annual estimated tax into four equal segments. The resulting payments are appropriate for the quarterly estimated taxes of taxpayers with a steady income, but this does not work as well for taxpayers whose income fluctuates. Some taxpayers may have a hard time finding the cash to pay estimated taxes in slower months.

Consider, for example, taxpayers Jane and John. Each of them owes $100,000 in annual estimated tax. Jane pays her estimated payments in four $25,000 installments per the regular installment method. She evenly earned her income, 25% each quarter, so the quarterly portions paid her estimated tax in full and on time. 

John’s earnings were uneven, with each tax quarter at 0%, 20%, 30%, and 50%, respectively. John may have a difficult time coming up with the cash necessary to make his first and second quarter estimated tax payments when his earnings are low. Using the regular installment method, if John were to pay less estimated tax in the first two quarters and more in the second two quarters, he would owe an underpayment penalty for the first two quarters.

The annualized income installment method allows John to refigure his installments, so they correlate to his income as he earns it. It does so by annualizing John’s installments over four overlapping periods. Each period begins on Jan. 1. The first period ends on March 31, the second ends on May 31, the third on Aug. 31, and the fourth period ends on Dec. 31. Each period includes all the previous periods, with the final period encompassing the entire year. It allows John to estimate his tax payments based on his income to that point in the year.

In this example, we know the exact percentage of John’s annual earnings from each tax quarter. John pays $0 in March, $20,000 in May, $30,000 in August, and $50,000 in December. John now has four installments of different amounts that, when added together, equal his full annual estimated tax of $100,000. John’s refigured installments are now paid on time, his underpayment penalties abated.

IRS Publication 505 has forms, schedules, and worksheets that guide taxpayers desiring to refigure their installments using the annualized income installment method. However, figuring installments this way is complicated and best done on an IRS worksheet by your favorite tax professional.