Premiums (1) Actuarial cost The Secretary shall, during September of each year beginning with 2020, determine a monthly actuarial rate for all enrollees under this section, which rate shall be applicable for months in the succeeding calendar year. Such actuarial rate shall be the amount the Secretary estimates to be necessary so that the aggregate amount for such calendar year with respect to those enrollees will equal the total amount which the Secretary estimates will be payable under this section for benefits accrued (including services performed and related administrative costs incurred) in such calendar year under the program under this section. In calculating the monthly actuarial rate, the Secretary shall make adjustments to take into account errors in estimations under this paragraph for previous years and shall include an appropriate amount for a contingency margin. (2) Premium (A) In general The monthly premium of each individual enrolled under this section for a month in a year shall be the monthly actuarial rate determined under paragraph (1) for months in such year. Such premium shall be community-rated and shall not vary among enrollees based upon the age, place of residence, or any other factors, except as provided under subparagraph (B). (B) Penalty for late enrollment In the case of an individual who does not enroll under this section in a period provided under paragraph (1) or (2) of subsection (b), the Secretary shall increase the monthly premium (in a manner similar to that applied under part B pursuant to section 1839(b)) of 10 percent for each full 12 months in which the individual could have been but was not so enrolled. In applying such an increase— (i) the aggregate percentage increase may not exceed 100 percent