Annualized Income Installment Method

The annualized income installment method is the alternative computation in Internal Revenue Code section 6654(d)(2) for the required estimated tax installment at each payment date. Instead of assuming that a quarter of the year's tax is due at each of the four dates, it looks at the income actually received through the end of each period, scales that up to an annual figure, computes the tax on it, and takes a stated percentage of that.

It is worked on Schedule AI of Form 2210, which is headed "Schedule AI—Annualized Income Installment Method." The method is the answer to a specific unfairness: someone paid mainly in the fourth quarter, or who realizes one large gain in November, is otherwise treated as having underpaid three installments they had no way of anticipating. Estimated taxes covers the default rule and the safe harbors that most people rely on instead; this page covers what happens when a taxpayer takes the other route.

The periods are not the payment quarters, and misreading them is the commonest mistake with this method. Schedule AI's four columns are headed 1/1 to 3/31, 1/1 to 5/31, 1/1 to 8/31 and 1/1 to 12/31, and the instructions state plainly that each period "includes amounts from the previous period(s)." So the second column covers five months from January 1, not the two months between April and May. Estates and trusts use a different set of end dates, running to February 28, April 30, July 31 and November 30.

The annualization multipliers follow from those lengths. Line 2 of the schedule carries 4, 2.4, 1.5 and 1, which convert three, five, eight and twelve months of income into a full-year figure. Estates and trusts use 6, 3, 1.71429 and 1.09091 instead, matching their own period ends.

The applicable percentages are 22.5%, 45%, 67.5% and 90%. These sit on line 20 and are simply a quarter, a half, three quarters and all of the 90% current-year test, which is what makes the annualized figure comparable to the installment it replaces.

Deductions annualize, and the standard deduction does not, which is a real asymmetry rather than a drafting quirk. A taxpayer who itemizes enters the itemized deductions actually paid in the period on line 4 and multiplies them by the same 4, 2.4, 1.5 and 1 on line 5. A taxpayer taking the standard deduction enters the full annual amount in every column on line 7, and line 8 takes the larger of the two. The practical consequence is that an early column is comparatively generous to the standard-deduction taxpayer, because three months of annualized income is being reduced by a full year's deduction.

Self-employment tax gets its own machinery. Line 15 pulls from line 36, which sits in Schedule AI Part II, a separate per-period computation of self-employment tax with its own prorated Social Security wage limits and its own annualization factors. Line 16 then adds other taxes for the period, "including, if applicable, Additional Medicare Tax and/or Net Investment Income Tax." A page that treats this method as an income tax calculation alone understates what it asks of a self-employed filer.

The recapture is the part people are surprised by, and it is arithmetic rather than a penalty. Lines 22 through 27 are worked one column at a time, and the instruction on the form is explicit: "Complete lines 22–27 of one column before going to line 22 of the next column." Line 24 enters 25% of the regular required annual payment. Line 25 carries forward what the previous column did not use. Line 26 adds the two, and line 27 takes the smaller of the annualized figure and that running total. The instructions describe the effect from the other direction: the schedule "selects the smaller of the annualized income installment or the regular installment (that has been increased by the amount saved by using the annualized income installment method in figuring any earlier installments)." So a light first installment makes the second one heavier by exactly the amount that was skipped.

Two commitments come with the election. The first is all or nothing: "If you use Schedule AI for any payment due date, you must use it for all payment due dates." The second is procedural. Form 2210's Part II box C reads: "Your income varied during the year and your penalty is reduced or eliminated when figured using the annualized income installment method. You must figure the penalty using Schedule AI and file Form 2210." The default posture, that the IRS computes the charge and sends a bill, is given up in exchange.

Box D is the neighbor worth knowing about and is a different remedy. It covers a taxpayer whose penalty is lower "when figured by treating the federal income tax withheld from your income as paid on the dates it was actually withheld, instead of in equal amounts on the payment due dates." That is an opt-out from the default even-spreading of withholding, which estimated taxes explains, and it helps the opposite kind of taxpayer: someone whose withholding was concentrated early rather than late.

Working one column, which is enough to see the pattern in all four.

1. Total the income actually received from January 1 to the period's end date, less adjustments to income, using the taxpayer's own method of accounting.

2. Annualize it by the column's multiplier: 4, 2.4, 1.5 or 1.

3. Subtract deductions. Annualized itemized deductions, or the full standard deduction, whichever is larger.

4. Figure the tax on the result, then add annualized self-employment tax from Part II and any other taxes for the period.

5. Apply the column's percentage: 22.5%, 45%, 67.5% or 90%.

6. Apply the running cap. Subtract what earlier columns have already claimed, then take the smaller of that figure and the regular installment increased by the amount earlier columns left unused.

An example, using the second column. Mireille's regular required annual payment for the year is $18,000, so the ordinary installment is 25 percent of that, or $4,500 per period. Her consulting income is back-loaded.

Through March 31 she has received $12,000. Annualized at the first column's multiplier of 4, that is $48,000. Assume, purely to make the arithmetic visible, that the total tax figured on that annualized amount comes to $10,000; the figure is stipulated for the illustration rather than derived from any rate table. The first column's applicable percentage is 22.5 percent, so $10,000 times 0.225 is $2,250. That is smaller than the $4,500 ceiling, so her first required installment is $2,250 rather than $4,500.

Through May 31 she has received $60,000. The second column's multiplier is 2.4, so the annualized figure is $144,000, and assume the tax on it comes to $40,000. The second column's percentage is 45 percent, giving $40,000 times 0.45, or $18,000. From that she subtracts the $2,250 already claimed in the first column, leaving $15,750.

Now the ceiling. The regular quarterly amount is $4,500, and the first column left $4,500 minus $2,250, or $2,250, unused. The ceiling for the second column is therefore $4,500 plus $2,250, or $6,750. She takes the smaller of $15,750 and $6,750, so her second required installment is $6,750.

Two periods in, she has been required to pay $2,250 plus $6,750, or $9,000, which is exactly what two flat installments of $4,500 would have required by the same date. The method changed when the money was due, not how much.

What it does well

• It sizes each installment against income the taxpayer had actually received, which is the honest measure for a seasonal business, a consultant paid on completion, or a year containing one large realized gain.
• It reaches self-employment tax, Additional Medicare Tax and net investment income tax through its own per-period computations, rather than covering the income tax alone.
• Entering the full standard deduction in every column gives real relief in the early periods to a taxpayer who does not itemize.
• It is available after the fact. The decision is made when the return is prepared, not in April of the year in question.

The costs

• It is four columns of a twenty-seven-line schedule, plus a second part for self-employment tax, and it requires income and deductions to be tracked by period rather than annually.
• Nothing is forgiven. A reduced early installment raises the ceiling on a later one by the same amount, so the method reschedules rather than reduces.
• Using it for one date commits the taxpayer to using it for all four.
• Electing it forfeits the default position that the IRS computes the charge and sends a bill: box C requires the taxpayer to figure the penalty and file Form 2210.
• It does nothing for a taxpayer whose income was level and who simply underpaid, which is the more common situation.