The default method is that you must pay in through estimated tax payments or withheld income taxes, the lower of 90% of your current year taxes or, if less, 100% of last year's taxes. The 100% rises to 110% if your prior year adjusted gross income was more than $150,000. Otherwise, you are subject to underpayment of estimated tax penalties, which is what TurboTax calculated 1/4 of this must be paid for each period: 1/1-3/31, 4/1-5/31, 6/1-8/31 and 9/1-12/31. For estimated tax payments, they are considered paid in the period if they are paid by the 15th of the month following the end of the period. If the 15th is a legal holiday, by the next business day.
You also have the option to avoid or reduce the penalties by having paid in sufficient taxes using the Annualized Income Installment Method. Form 2210 page 3. Under this method, which must be used for all periods, if used for any period, you must calculate the income taxes on the annualized cumulative taxable income through the end of each of the periods above and then deannualize the tax using line 20 on the form.
You can use this method for 2025. TurboTax will automatically calculate for the last period because that's what is on your return.
TurboTax is of no help in computing the taxes for the first three periods.
