42 CFR §408.24

1. (a)Enrollment. For an individual who first enrolled before April 1, 1981 or after September 30, 1981 and before January 1, 2023, the period includes the number of months elapsed between the close of the individual's initial enrollment period and the close of the enrollment period in which he or she first enrolled, and excludes the following:
   1. (1)The three months of January through March 1968, if the individual first enrolled before April 1968.
   2. (2)Any months before January 1973 during which the individual was precluded from enrolling or reenrolling by the 3-year limitation on enrollment or reenrollment that was in effect before October 30, 1972.
   3. (3)Any months in or before a period of coverage under a State buy-in agreement.
   4. (4)For an individual under age 65, any month before his or her current continuous period of entitlement to hospital insurance.
   5. (5)For an individual age 65 or older, any month before the month he or she attained age 65.
   6. (6)For premiums due for months beginning with September 1984 and ending with May 1986, the following:
      1. (i)Any months after December 1982 during which the individual was—
         1. (A)Age 65 to 69;
         2. (B)Entitled to hospital insurance (Medicare Part A); and
         3. (C)Covered under a group health plan (GHP) by reason of current employment status.
      2. (ii)Any months of SMI coverage for which the individual enrolled during a special enrollment period as provided in § 407.20 of this chapter.
   7. (7)For premiums due for months beginning with June 1986, the following:
      1. (i)Any months after December 1982 during which the individual was:
         1. (A)Age 65 or over; and
         2. (B)Covered under a GHP by reason of current employment status.
      2. (ii)Any months of SMI coverage for which the individual enrolled during a special enrollment period as provided in § 407.20 of this chapter.
   8. (8)For premiums due for months beginning with January 1987, the following:
      1. (i)Any months after December 1986 and before October 1998 during which the individual was:
         1. (A)A disabled Medicare beneficiary under age 65;
         2. (B)Not eligible for Medicare on the basis of end stage renal disease, under § 406.13 of this chapter; and
         3. (C)Covered under an LGHP as described in § 407.20 of this chapter.
      2. (ii)Any months of SMI coverage for which the individual enrolled during a special enrollment period as provided in § 407.20 of this chapter.
   9. (9)For premiums due for months beginning with July 1990, the following:
      1. (i)Any months after December 1986 during which the individual met the conditions of paragraphs (a)(8)(i)(A) and (a)(8)(i)(B) of this section, and was covered under a GHP by reason of the current employment status of the individual or the individual's spouse.
      2. (ii)Any months of SMI coverage for which the individual enrolled during a special enrollment period as provided in § 407.20 of this chapter.
   10. (10)For premiums due for months beginning with January 1, 2007, the following:
       1. (i)Any months after December 2006 during which the individual met the conditions under § 407.21(a) of this chapter.
       2. (ii)Any months of Part B (SMI) coverage for which the individual enrolled during a special enrollment period as provided in § 407.21(b) of this chapter.
2. (b)Enrollment on or after January 1, 2023. For an individual who first enrolled on or after January 1, 2023, the period includes the number of months elapsed between the close of the individual's initial enrollment period and the close of the month in which he or she first enrolled and excludes—
   1. (1)The periods of time described in (a)(1) through (10) of this section; and
   2. (2)Any months of non-coverage in accordance with an individual's use of an exceptional conditions SEP under § 407.23 of this subchapter provided the individual enrolls within the duration of the SEP.
3. (c)Reenrollment. For an individual who reenrolled before April 1, 1981, or after September 30, 1981, and before January 1, 2023, the period—
   1. (1)Includes the following:
      1. (i)The number of months elapsed between the close of the individual's initial enrollment period and the close of the enrollment period in which he or she first enrolled; plus
      2. (ii)The number of months elapsed between the individual's initial period of coverage and the close of the enrollment period in which he or she reenrolled; plus
      3. (iii)The number of months elapsed between each subsequent period of coverage and the close of the enrollment period in which he or she reenrolled.
   2. (2)Excludes the following:
      1. (i)Any of the periods specified in paragraph (a) of this section; and
      2. (ii)Any month before April 1981 during which the individual was precluded from reenrolling by the two-enrollment limitation in effect before that date.
4. (d)Reenrollment on or after January 1, 2023. For an individual who reenrolled on or after January 1, 2023, the period—
   1. (1)Includes the number of months specified in paragraphs (c)(1)(i) through (iii) of this section; and
   2. (2)Excludes—
      1. (i)The number of months specified in paragraphs (c)(2)(i) and (ii) of this section; and
      2. (ii)Any months of non-coverage in accordance with an individual's use of an exceptional conditions SEP under § 407.23 of this subchapter provided the individual enrolls within the duration of the SEP.