How to make one time additional estimated tax payment?

[superlyc]

I made some unexpected capital gain later this year. And my regular tax withheld from paycheck does not seem to be enough. I am concerned I will underpay the tax this year. I wonder how should I make one time payment to the IRS? Is this called estimated tax payment?
If so, which form should I choose to pay for? 1040? or 1040ES? And how should I file this with TurboTax later next year? Do I get a form to import to TurboTax?

[Bsch4477]

Yes, it’s an estimated payment and the details are here with a link to the 1040-ES form. When you do your return you report the payment in your TurboTax program.

[superlyc]

So, I should choose 1040 ES? How should I report this with Turbox then? I never did this before so. Is there a tax form to upload to Turbox after I made this estimated tax payment?

[Bsch4477]

Yes. Send the completed 1040-ES Form with your check to the IRS. There’s nothing else to do. The TurboTax program has an area in the program for you to report your payment and the program puts that amount in the proper line in your return. You don’t have to do anything else. 

[superlyc]

Thank you. I found the IRS provide direct pay online. In that way, I don't have to mail it right? And as long as it is done before the end of the year, it is good, right?

[NCperson]

@superlyc yes, you can just pay online.

Quarterly payments are due by January 15, 2026.  if the capital gains occured after August 31, 2025 and you pay the estimate by January 15, 2026, that solves a lot of issues. 

if the gain occured prior to Sept 1, the answer is alot more complicated, and in that case, pay the estimate TODAY. 

[baldietax]

Yes pay directly online at irs.gov, avoid mailing checks/vouchers if possible.  Be sure to designate it as 1040-ES for the correct tax year.  When you file under Deductions & Credits there is a section to input any ES paid.

But just paying one-off ES in November may not protect you from a penalty at this point, or may not even be needed depending your situation.  See Form 2210 Lines 1-9 for the safe harbor calculation, you need to have paid (via withholding at any time during the year, or "timely" ES - usually quarterly) - the smaller of 100% of your 2024 tax (110% if AGI > 150k or 75k if filing MFS), or 90% of your 2025 tax.  If you've already met the safe harbor thru withholding for 100/110% of your 2024 tax then you don't need to pay ES regardless the size or timing of your gains, and just owe the balance of the 2025 tax due in April.

If you do owe ES to meet the safe harbor amount, then by default it's due in quarterly installments so a one-off payment will be considered largely late; it may stop the penalty accruing further but won't eliminate it.  If the income occurred unevenly thru the year and in particular later in the year, you can try to reduce the penalty when you file using the Annualized Income method on Form 2210.  When you first put your return together TT will calculate the default penalty, check line 38 on your 1040, then you can try and reduce it thru Other Tax Situations / Underpayment Penalties.  The other option to avoid ES penalty is to increase withholding to cover the safe harbor amount, it doesn't matter the timing, but it's probably too late in the year for this to have much impact via W2.

See this recent thread for more on the same topic

https://ttlc.intuit.com/community/taxes/discussion/re-paying-capital-gains-tax-on-stock-investments/...

[Bsch4477]

That works. 

[superlyc]

@baldietax @NCperson  Thank you

I have two parts of large capital gains. One occurred before August 31. Another is around Oct 30. If with only the first part, I estimated that I am OK, because I increased per paycheck withholding. However, the Oct sale is not planned. And with this second part of capital gains, I will probably owe some tax at end of the year. Now I want to know if I can pay this ahead and avoid penalty.

One question is since I did not know I will make the second part of my capital gains and I would not expect I will have to pay additional tax, why will I be considered late for paying estimated tax for previous quarter?

Another is I did not set up estimated tax beginning this year, can I still pay that for one time?

Thank you

[NCperson]

@superlyc - it gets complicated.... the IRS expects to get paid quarterly and unless you complete form 2210 (which is a pain in the neck), it assumes your income was earned evenly spread through out the year. 

you can pay ahead to avoid any penalty.  The due date for income generated between Sept 1 and Dec 31 is January 15, 2026.  But the IRS will always take money early! 

[baldietax]

@superlyc I would check the safe harbor, from what you describe with your increase in withholding already, maybe you met 2024 tax and you don't have to worry about estimated tax.

to @NCperson's point Form 2210 AI method is a pain but provides that ability to handle unexpected income late in the year to line up with one-off ES.  Q4 Roth conversions is another example.  IRS still expects you to plan and pay tax timely.  The 'pain' in the AI method is you have to calculate your AGI, withholding, qualified divs and LTCG by quarter (3/31, 5/31, 8/31, 12/31) which TT can't do automagically, you have to work all that out and input it.

[superlyc]

 @NCperson @baldietax  thank you again.

Follow up questions,
1 I think I need go online and select 2025 1040 ES and pay, right?
2 What proof will I get and must file with my return after I made this estimated payments? Never done this before. Just want to double check before I do that in case missing something important.
3 Since it is already in November, does it matter whether I make that one time estimated tax payment now or later towards the end of the year?
4 If 2210 is too complicated for me, can I still use TurboTax?  Maybe just pay a little more interests. Maybe it is still cheaper than a CPA?  Or is the real CPA offered by TurboTax another option? I am not sure if they offer to do this.

thank you so much

[VolvoGirl]

#1 Yes  you can pay directly on the IRS website https://www.irs.gov/payments

Be sure to pick the right kind of payment and year.....2025 Estimate

#2 when you file next year you just enter the date you paid and the amount.   It is easy.   It will be under Federal > Deductions & Credits > Estimates and Other Taxes paid

#4  Turbo Tax will automatically fill out Form 2210 if you have a penalty.   If you do have a penalty….you might be able to eliminate it or at least reduce it.  You can go to Federal Taxes tab or Personal tab, under Other Tax Situations and select Start by the Underpayment Penalties. You will answer a series of questions that may reduce or eliminate the penalty. Or you can elect to have the IRS figure the penalty for you.  It's form 2210.

[NCperson]

@superlyc #2 - your proof is the email confirmation that the IRS sends you and the debit in your bank account statement and it would be listed on your IRS transcript. 

#3 - if you are going to owe an underpayment penalty, then pay now as it will cut off the accumulation of interest charges.  Otherwise, pay by January 15, 2026. 

#4 - a CPA is unlikely to be cheaper.  Just pay your estimate now and then assess what the underpayment penalty looks like.   It is possible there would be no penalty due to the 'safe harbor' option.

[superlyc]

Thank you all. Another thing that I am confused is:
My understanding is if I still can make extra tax withheld through my regular paycheck, I do not need to worry about this. However, if I can not have enough withheld through the rest of the year with paycheck and I have to make estimated payment, I may possibly pay penalty because I did not make payments in the previous quarters. The part confuses me is that I am may end up paying same amount of tax at the end of the year, through pay check I don't have to pay penalty, while through estimated tax, I may need to.  This idea is hard for me to understand.

If my understanding is correct, will it make any difference if I try to let my employer withhold as much as possible for the rest of the year and still pay some amount of estimated tax. Will it potentially same me some money compared to only through estimated tax payments?