AMT and Long-Term Capital Gain

By Kaye A. Thomas
Current as of December 24, 2014

Even if you don’t usually pay alternative minimum tax, a large long-term capital gain can result in AMT liability. Here’s why.

There’s no reason to believe Congress intended the alternative minimum tax to apply merely because you have a long-term capital gain. The law provides that the lower rates for these gains (and for qualified dividends) apply under the AMT as well as the regular income tax. The way it works out, though, you may still pay AMT because of a large long-term capital gain.

The AMT exemption

A major reason for paying AMT in the year of a large capital gain is the AMT exemption. This is a special deduction that’s designed to prevent the alternative minimum tax from applying at lower income levels. The problem is that the AMT exemption is phased out when your income goes above a certain level. For this purpose, capital gain is considered income, so it can reduce or eliminate your AMT exemption.

For example, if you’re single and your income under the AMT rules is $119,200 or less, you’re allowed an AMT exemption of $53,600. (These amounts are for 2015; they’re adjusted each year for inflation.) Normally that’s enough to prevent you from paying AMT unless you’re able to claim unusually large tax benefits that reduce your regular tax. But suppose your income is around that level before you add a $200,000 capital gain (sale of a real estate investment, or stock, or perhaps sale of a business you built up). Your tax on the capital gain is the same under both the regular tax and the AMT. Under the AMT, though, the added income wiped out $50,000 of your AMT exemption. In the AMT calculation, it’s as if you added not only $200,000 of capital gain but also another $50,000 of ordinary income.

How big is the effect? The answer depends on how close you are to paying AMT before this happens. Overall, a large capital gain can cause you to incur $10,000 or more of AMT.

Do the math

Here’s how it works for someone with income below the level where the 20% capital gains rate kicks in. For every $1,000 of added long-term capital gain, your regular income tax goes up by $150 (15%). When we move over to the AMT, the same $1,000 is taxed at 15%, but in addition eliminates $250 of your exemption amount, because the exemption is phased out at a rate of 25%. The exemption amount is used to reduce the amount of tax you pay on your ordinary income (the income that is taxed at either 26% or 28% under the AMT). So your tax under the AMT rules goes up by about $70, which is 28% of this added $250. You didn’t really add another $250 of income, but your exemption amount went down by $250, and that exposed another $250 of your existing income to tax under the AMT.

Result? Under the AMT, adding $1,000 of long-term capital gain can increase your tax by as much as $220, consisting of the $150 tax on the gain itself and the $70 that hits you because the exemption amount is reduced. In effect, you’re paying 22% on the gain under the AMT and 15% on the gain under the regular income tax, so a big capital gain can lead to a big AMT bill.

That doesn’t necessarily mean you pay AMT every time you have a long-term capital gain. Most people have at least a little bit of a cushion between the amount of regular tax they pay and the level where they would have to start paying alternative minimum tax. (The size of your cushion depends on various items. See Top 10 Things that Cause AMT Liability.) Besides, the capital gain can cause some tax benefits to phase out under the regular tax, too. But there’s a good chance you’ll pay AMT if your income is in the range where the exemption amount is phased out and you have a large long-term capital gain.

Another factor

If you pay state income tax on your capital gain, and claim that tax as an itemized deduction, the capital gain can boost your AMT even more. For example, if your state tax rate is 10% and your federal capital gain rate is 20%, the effective rate of tax on this gain under the regular income tax may be 18%. Under the AMT, you’re paying 20% on the capital gain plus 7% caused by phasing out your exemption, with no deduction for state income tax, so your effective rate is 27%. In this scenario, your effective federal tax rate for the capital gain is nine percentage points higher under the AMT than under the regular income tax.

It can be even worse. The itemized deduction for state income tax can be used against ordinary income that’s taxed at 39.6%, which means the effective rate of tax on the capital gain under the regular income tax could be about 16% versus 27% in the AMT calculation, producing a difference of eleven percentage points.

More bad news

There’s more bad news. People who get caught by the AMT because of a large long-term capital gain usually don’t qualify for the AMT credit in later years. The AMT is being caused by items that aren’t considered timing items. Possibly you have some timing items in addition to the large capital gain, and in that case at least part of your AMT would be available as a credit in later years. Typically this added tax is just a dead loss.

What to do

In many cases there isn’t a lot you can do about this added tax. Sometimes, though, if you’re aware of the issue, you may be able to take measures to reduce the impact.

Timing your capital gains

In some situations you can control the year in which you report capital gains. You may be able to delay a sale until after the end of the year, or spread the gain over a number of years by using an installment sale. There’s no simple answer to whether these measures help or hurt, so someone has to sharpen a pencil and grind out some numbers.

For example, your gain may be at a level where spreading it over a number of years will keep you out of the AMT — or at least reduce the impact. In this case an installment sale might be an attractive alternative. But suppose your gain is so large that it will phase out your AMT exemption amount many times over. In this situation, you may get a better result by reporting all the gain in one year, so it affects only one year’s exemption amount.

Timing other items

Another way to plan for the AMT is to see if you can change the timing of other items that are affected by the tax. For example, if you make estimated payments of state income tax, you may try to schedule your payments so they don’t fall in the same year as your large capital gain. In some cases you may come out ahead even if you incur a small penalty for being late with your state estimated payment.