42 CFR §407.57

1. (a)Deemed enrollment. An individual whose Part A entitlement ends in accordance with § 406.13(f)(2) of this subchapter on or after January 1, 2023, is deemed to have enrolled into the Part B-ID benefit effective the first day of the month in which the individual first satisfies § 407.55, provided he or she provides the attestation required under § 407.59 prior to the termination of their Part A benefits.
2. (b)Individual enrollment. An individual whose Part A entitlement ends in accordance with § 406.13(f)(2) of this subchapter, and who meets the requirements of § 407.55 and provides the attestation required under § 407.59, may enroll in the Part B-ID benefit under the following conditions:
   1. (1)If the individual's entitlement ends prior to January 1, 2023, he or she may enroll in the Part B-ID benefit beginning on October 1, 2022.
   2. (2)If individual's entitlement ends on or after January 1, 2023, the individual may enroll at any time after their entitlement ends.
3. (c)Reenrollment. An individual who had previously enrolled in the Part B-ID benefit, but terminated that benefit, can reenroll at any time, provided the individual meets the requirements of § 407.55 and provides the attestation required under § 407.59.
4. (d)Attestation. To enroll in the Part B-ID benefit, an individual must submit the required attestation as described in § 407.59.
5. (e)Entitlement date. The entitlement to the Part B-ID benefit will start as follows:
   1. (1)For enrollments provided under paragraph (a) of this section, entitlement is effective the month Part A benefits are terminated.
   2. (2)For enrollments provided under paragraphs (b) and (c) of this section, the Part B-ID benefit is effective the month following the month in which the individual provides the attestation required in § 407.59.
   3. (3)Exception. Enrollments submitted October 1, 2022 through December 31, 2022, are effective January 1, 2023.