(a) General. We have four different rules for determining if you are insured for purposes of establishing a period of disability or becoming entitled to disability insurance benefits. To have disability insured status, you must meet one of these rules and you must be fully insured (see § 404.132 which tells when the period ends for determining the number of quarters of coverage (QCs) you need to be fully insured).

(b) Rule I—You must meet the 20/40 requirement. You are insured in a quarter for purposes of establishing a period of disability or becoming entitled to disability insurance benefits if in that quarter—

(1) You are fully insured; and

(2) You have at least 20 QCs in the 40-quarter period (see paragraph (f) of this section) ending with that quarter.

(c) Rule II—You become disabled before age 31. You are insured in a quarter for purposes of establishing a period of disability or becoming entitled to disability insurance benefits if in that quarter—

(1) You have not become (or would not become) age 31;

(2) You are fully insured; and

(3) You have QCs in at least one-half of the quarters during the period ending with that quarter and beginning with the quarter after the quarter you became age 21; however—

(i) If the number of quarters during this period is an odd number, we reduce the number by one; and

(ii) If the period has less than 12 quarters, you must have at least 6 QCs in the 12-quarter period ending with that quarter.

(d) Rule III—You had a period of disability before age 31. You are insured in a quarter for purposes of establishing a period of disability or becoming entitled to disability insurance benefits if in that quarter—

(1) You are disabled again at age 31 or later after having had a prior period of disability established which began before age 31 and for which you were only insured under paragraph (c) of this section; and

(2) You are fully insured and have QCs in at least one-half the calendar quarters in the period beginning with the quarter after the quarter you became age 21 and through the quarter in which the later period of disability begins, up to a maximum of 20 QCs out of 40 calendar quarters; however—

(i) If the number of quarters during this period is an odd number, we reduce the number by one;

(ii) If the period has less than 12 quarters, you must have at least 6 QCs in the 12-quarter period ending with that quarter; and

(iii) No monthly benefits may be paid or increased under Rule III before May 1983.

(e) Rule IV—You are statutorily blind. You are insured in a quarter for purposes of establishing a period of disability or becoming entitled to disability insurance benefits if in that quarter—

(1) You are disabled by blindness as defined in § 404.1581; and

(2) You are fully insured.

(f) How we determine the 40-quarter or other period. In determining the 40-quarter period or other period in paragraph (b), (c), or (d) of this section, we do not count any quarter all or part of which is in a prior period of disability established for you, unless the quarter is the first or last quarter of this period and the quarter is a QC. However, we will count all the quarters in the prior period of disability established for you if by doing so you would be entitled to benefits or the amount of the benefit would be larger.