A distribution on October 20, 2020 is 4th-quarter income. The deadline for making an estimated tax payment for the 4th quarter of 2020 is January 15, 2021.
Because by default the calculation of any underpayment of taxes throughout the year assumes that income is received uniformly throughout the year, you might have to annualize income on Schedule AI of Form 2210 to reduce or eliminate penalties for quarters 1 through 3.
