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Estimated Tax on Unplanned Capital Gains
In general, you are expected to pay all the money you owe in taxes by the end of the tax year, or you may have to pay a penalty. But you don't have to pay a penalty if: The amount you owe (i.e. total tax due minus what you paid in withholding and estimated taxes) is less than $1000. You paid at least 90% of your total tax bill. You paid at least 100% of last year's tax bill. https://www.irs.gov/taxtopics/tc306.html I think point #3 may work for you here. Suppose that last year your total tax liability was, say, $5,000. This year your tax on your regular income would be $5,500, but you have this additional capital gain that brings your total tax to $6,500. If your withholding was $5,000 -- the amount you owed last year -- than you'll owe the difference, $1,500, but you won't have to pay any penalties. If you normally get a refund every year, even a small one, then you should be fine. I'd check the numbers to be sure, of course. If you normally have to pay something every April 15, or if your income and therefore your withholding went down this year for whatever reason, then you should make an estimated payment. The IRS has a page explaining the rules in more detail: https://www.irs.gov/help-resources/tools-faqs/faqs-for-individuals/frequently-asked-tax-questions-answers/estimated-tax/large-gains-lump-sum-distributions-etc/large-gains-lump-sum-distributions-etc