I repositioned my investments and sold a large quantity of stock in the first quarter of this year. As such, for the first time in a long time, I will need to pay estimated taxes. However, I am not sure how estimated taxes work and I am finding the literature assumes a lot about my knowledge. I have a few clarifying questions about the overall system behind estimated tax payments.

  1. I noticed that it is possible to pay all of one’s estimated taxes in one go on the first quarterly payment deadline. Is it possible to make a lump payment at any time other than for the first installment?
  2. I missed the first quarterly payment deadline and I didn't follow the IRS’s description of how to calculate penalties. Is there a calculator somewhere?
  3. I am an expatriate and wasn’t required to pay income tax last year. Is this helpful for avoiding penalties? I thought I saw some verbiage indicating that penalties are related to a percentage of last year's taxes.

Thank you in advance!

  • Someone else will probably write an answer but this might help point you in a direction. I vaguely remember that to be assessed a penalty, you need to underpay your annual tax liability by more than 10% for a second year consecutively. So single year spikes in income don't trigger the requirement to send payment estimates. I had to once, and I just did a quick back of the envelope calculation then sent a payment, likely annual AGI + net misc income causing the spike * probable tax rate then rounded up a bit to be safe. But that was only after I had blown this the year before.
    – quid
    Commented Apr 28, 2021 at 21:42

1 Answer 1


Dupe at least
One-time estimated tax payment for windfall
estimated IRS tax payments
At what time do you have to pay capital gains taxes in the US to avoid any penalties?
Withholding for unexpected Short-Term Capital Gains and Penalties
Estimated Tax on Unplanned Capital Gains
Difficult time understanding 1040-ES and Late Payments Penalties

If you are still a US citizen but living elsewhere and filing returns, but not owing tax perhaps because substantially all your income is excluded by the Foreign Earned Income Exclusion, then you are in one of the safe harbors for estimated tax. Specifically, if you reported zero tax liability for the prior year (2020) -- this is line 24 on 1040, with adjustments in some relatively rare cases -- and that return was for a full year, your minimum required in-year payment for 2021 is zero, nothing, nada, nil.

The usual alternatives, to which you may have seen reference, are that to avoid the underpayment penalty you must pay (by withholding, timely estimated payments, or any combination) either 90% of this year's tax (which at present you don't know, and you may be able to estimate well or poorly) or 100% of last year's tax (which you do or soon will know) on a full-year return as above, increased to 110% if last year's AGI was over $150k. See Form 1040-ES and its attached instructions which you can download. If you underpay, the penalty is proportional to the amount and time duration of the underpayment, and thus indirectly to either this year's tax or last year's tax whichever gives the lesser payment requirement.

You can of course still make a payment(s?) if you want -- you will need to pay not later than next April (to avoid interest, although filing from out of country you don't get the additional failure-to-pay penalty until June), and if you don't have a better use for the money in the meantime, there's no harm in paying now.

Be advised in the US tax context 'expatriation' means something quite different from just living elsewhere: if you renounced your citizenship (or had naturalization revoked), or in some cases relinquished, abandoned or had revoked your "green-card" (lawful permanent resident) status, with a net worth of at least $2 million or income averaging for the previous 5 years at least an inflation-adjusted amount currently $171,000. Such a person is subject to a special tax described here and in more detail in pub 519 but NOT to the normal 'citizen' or 'resident' income tax, since after expatriating you are neither of those.

Also, remember FBARs are required for accounts over $10k regardless of any tax or tax filing

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