The distribution is taxable income and the tax may be due this quarter. Check the safe harbor rule first because it may mean nothing is due until April.
Cashing out an inherited traditional IRA adds the whole distribution to your taxable income for the year, and custodians often withhold only 10% or nothing at all. The gap between that and your real bracket is the surprise, and it can be large.
Before sending the IRS anything, check the safe harbor rule. If your withholding and payments this year already reach 100% of last year's total tax, or 110% if your prior-year adjusted gross income was over $150,000, no estimated payment is required for the windfall. You would pay the balance in April with no penalty at all.
If safe harbor does not cover you, the tax on the distribution is due with the quarterly deadline for the period you received it, not in April. The annualized income method keeps the earlier quarters from being penalized for income that did not exist yet.
One more rescue if it is late in the year. Extra withholding from a W-2 paycheck, or from the distribution itself if your custodian allows a higher rate, is treated as paid evenly across the whole year, which can cover the bill without any quarterly paperwork.
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Sources: IRS Publication 590-B· IRS Publication 505