in terms of making the payments you can do that direct at irs.gov, be sure to give the correct classification as estimated tax and 2025 tax year.
to avoid underpayment penalty you need to pay thru withholding or timely (quarterly) estimated tax, the smaller of 100% of your 2024 tax (110% if your AGI > 150k or 75k for MFS filing status), or 90% of your 2025 tax. That's your safe harbor amount. See lines 1-9 on Form 2210 for the calculation. Withholding is always considered "timely" but estimated tax needs to be paid quarterly.
If you had a significant increase in tax for 2025 then you may be better off paying ES based on 2024 tax depending your situation, first step is to make that calculation. Paying based on 2024 is the simplest calculation since the tax is known, the only variable is 2025 withholding, and it doesn't matter how much your 2025 income is or when it occurs, but it can often be an overpayment if you fall into that 110% high income requirement, or your income is flat or declines from year to year. If you filed with TT with 2024 it would have produced estimated tax vouchers (which you don't need to follow) based on 100/110% of 2024 tax as default and assuming your 2025 withholding is the same as 2024.
Whether you pay quarterly ES based on 2024 or 2025, if you didn't pay ES for Q1/2 already but now it's July, you will incur a penalty, but you can stop the penalty from accruing if you catch up that missed quarterly payments now, and make the 3rd payment by the Q3 deadline etc.
The other option, if your additional investment income is uneven and more towards the later half of the year, you can pay ES unevenly to line up with it (another good example is a Roth conversion in December that couldn't be planned in quarterly ES payments thru the year) and then file Form 2210 Annualized Income method, but you will need to calculate your AGI, Qualified Dividends, Long Term Cap Gain etc for each quarter (3/31, 5/31, 8/31). This is handled in TT under Other Tax Situation / Underpayment Penalty when you file next year. But if your income is incurred evenly thru the year, this method may not help eliminate the penalty as it will still show that you were late paying ES that were actually due in Q1-2.
More info see https://www.irs.gov/faqs/estimated-tax and https://www.irs.gov/pub/irs-pdf/i2210.pdf
Not a CPA please research accordingly, hope this helps.
