Lumpy Income? Use Schedule AI to Cut Your Underpayment Penalty

Quarterly estimated tax payments assume you earn the same amount every three months. Plenty of freelancers don't. A designer whose $60,000 project pays out in October has earned almost nothing for nine months, yet the IRS schedule still expects a quarter of the year's tax on April 15.

A rule exists for exactly this. Form 2210 includes Schedule AI, the annualized income installment method, which lets you size each payment to the income you had actually earned by its due date. It can cut an underpayment penalty by hundreds of dollars, and it sits on a form many freelancers never open.

1.Why Equal Payments Overcharge Lumpy Income

The standard schedule splits your required annual payment into four equal installments, due April 15, June 15, September 15, and January 15. The required annual payment is the smaller of 90% of this year's tax or a safe-harbor amount based on last year's return (a rule that protects you from the penalty). Pay less than an installment by its due date and the IRS charges an underpayment penalty, which works like interest on the shortfall for every day it stays unpaid.

Equal installments fit a steady paycheck. They fit poorly when a seasonal business earns most of its income in the last four months. Four kinds of freelancers tend to hit this:

• Seasonal workers. A wedding photographer books most of the year's income between May and October.
• One big late project. A developer finishes a contract in November and gets paid in a single lump.
• Slow starters. A new freelancer lands the first clients in the spring and doubles the pace by fall.
• Late launches. A writer releases a course in December after eleven slow months.

2.How Annualizing Works, Period by Period

Annualizing scales up what you've earned so far to a full year, as if the rest of the year would look the same. Schedule AI does this four times, using income through four cutoff dates.

The multipliers come from dividing 12 by the months counted: 3 months gives 4, 5 months gives 2.4, and 8 months gives 1.5. For each row you multiply your net profit so far, figure the tax on that full-year number, and take the percentage shown. Then subtract what the earlier rows already required. The form also annualizes your self-employment tax, the 15.3% Social Security and Medicare tax you pay on top of income tax.

Notice that the cutoffs are May 31 and August 31, not the end of a calendar quarter. A profit report run on June 30 won't give you the right number for the second row.

3.A Worked Example: $80,000 Earned Mostly in the Fall

To keep every step checkable, assume a flat 25% total tax rate on net profit, income tax and self-employment tax together. Real returns use tax brackets, so your own numbers will differ. The form's steps are the same, though. Say a freelancer ends the year with $80,000 in net profit, which makes the year's tax $20,000 and the required annual payment 90% of that, or $18,000. Net profit by each cutoff looks like this: $5,000 by March 31, $10,000 by May 31, $20,000 by August 31, and $80,000 by December 31.

Method A: equal installments

The standard schedule requires $4,500 on each of the four dates, so $4,500 by April 15, $9,000 total by June 15, and $13,500 by September 15.

Method B: Schedule AI

April 15: $5,000 times 4 is $20,000, which carries $5,000 of tax at 25%, and 22.5% of that is $1,125 required. June 15: $10,000 times 2.4 is $24,000, which carries $6,000 of tax, and 45% is $2,700 total, so $1,575 is new. September 15: $20,000 times 1.5 is $30,000, which carries $7,500, and 67.5% is $5,062.50 total, so $2,362.50 is new. January 15: the full $80,000 carries $20,000, and 90% is $18,000 total, so the last installment is $12,937.50.

Now suppose this freelancer paid nothing until January 15, then sent the full $18,000 in one payment. The IRS sets the penalty rate each quarter. Assume 8% a year to keep the arithmetic simple. Under Method A, three $4,500 installments were late by about 9, 7, and 4 months, for $4,500 times 8% times 20 months divided by 12, or $600. Under Method B, the late amounts were $1,125, $1,575, and $2,362.50, which adds up to about $204. The penalty drops by $396.

Schedule AI lets each payment follow the income you had earned by its due date.

4.What to Keep and How to File

Schedule AI asks for records most freelancers don't have ready: net profit through four specific dates. Set those up as you go.

• Profit reports on the four cutoffs. Run a profit and loss report for Jan 1 to Mar 31, May 31, Aug 31, and Dec 31.
• Income by the date you were paid. Cash-method freelancers count income when it lands in the bank account, so a December invoice paid in January belongs to next year.
• Expenses by the date you paid them. A $3,000 laptop bought in September lowers profit only in the last two periods.
• Form 2210 attached to your return. The IRS requires you to file it when you use the annualized method. If you use Schedule AI for one due date, you use it for all four.

5.When to Skip It

Schedule AI adds paperwork, so use it only when it saves something. If you paid in at least as much as last year's total tax, the safe-harbor rule already protects you from the penalty and there's nothing to reduce. The same goes for freelancers whose income really is level all year.

Using the method is a choice the tax code hands you, and taking it is legal planning. Judge Learned Hand, one of the most-cited appeals judges in US history, wrote in the 1934 tax case Gregory v. Helvering (69 F.2d 809): "Anyone may so arrange his affairs that his taxes shall be as low as possible; he is not bound to choose that pattern which will best pay the Treasury." The Supreme Court later reversed the result of that case, but the line about lowering your own tax bill within the rules is still quoted today.

If you've already missed installments this year, the steps in Missed a Quarterly Tax Payment? Here's What to Actually Do apply first, and Schedule AI can shrink the penalty afterward.

Equal quarterly payments were written for equal quarterly income. Freelancers who earn in lumps can ask the IRS to count the income they actually had on each due date, and Form 2210 is where that request goes.

If you want to see what your own lumpy year would owe before you choose a method, the free tax checkup at simplance.org/tax-checkup estimates your tax from the income and expenses you've already recorded.