Q&A: How to figure your capital gains tax bite so the IRS doesn’t zap you

Dear Liz: We had big capital gains this year, and we owe taxes plus a penalty for not paying estimated taxes. Is there a way to plan ahead for taxes since every year is different regarding gains or losses? I know one option is to just pay estimated taxes quarterly based on the previous year’s gains. Apparently the mutual fund companies don’t automatically withhold the taxes.

Answer: Our tax system is “pay as you go,” which means the IRS expects you to pay taxes as you earn or receive income. If you fail to do so and your tax bill is more than $1,000, you may face penalties.

As you rightly note, though, you won’t know what your total capital gains or losses will be until year’s end. You wouldn’t want to pay taxes on a big gain one quarter only to have a big loss the following quarter. You can avoid the penalties by making sure your withholding and estimated tax payments equal at least 100% of the total tax you paid in the previous tax year if your income is $150,000 or less. If your income is over $150,000, your payments and withholding should equal at least 110% of last year’s taxes.

The alternative is to pay at least 90% of the tax you’ll owe on your estimated income for the current year. A tax pro can help you figure out how much you need to pay as well as offer tips for reducing your tax bill.