Stock options windfall - when to pay estimated taxes?

[gsu13]

A good problem to have is that we got a mid-7 figure windfall when stock options vested and exercised on June 18 - a few days after the June 15th estimated tax payment.  So are estimated taxes due on Sept 15?  And is that 75% of capital gain taxes due?   

Meanwhile, I could keep that in a high-interest money market earning 5.30% and then pay in September?

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[removed]

@gsu13 

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What is your 2023 tax ? Do you have withholding?

If your total 2024 withholding alone is 100 % of that amount ( x 1.10 if your 2023 AGI is over $150,000),

or 90% of the 2024 tax, you can avoid any penalty  in 2024.

(in case of a windfall, the 90% level is unlikely to be met, unless extraordinary action is taken).

You don't need to make estimated tax payments.

@gsu13