20 C.F.R. § 404.1560
When we will consider your vocational background
(a) General. If you are applying for a period of disability, or disability insurance benefits as a disabled worker, or child's insurance benefits based on disability which began before age 22, or widow's or widower's benefits based on disability for months after December 1990, and we cannot decide whether you are disabled at one of the first three steps of the sequential evaluation process (see § 404.1520), we will consider your residual functional capacity together with your vocational background, as discussed in paragraphs (b) and (c) of this section.
(b) Past relevant work. We will first compare our assessment of your residual functional capacity with the physical and mental demands of your past relevant work. See § 404.1520(h) for an exception to this rule.
(1) Definition of past relevant work—(i) What is past relevant work. Past relevant work is work that you have done within the past five years that was substantial gainful activity and that lasted long enough for you to learn to do it (see § 404.1565(a)). We will not consider work to be past relevant work if you started and stopped it in fewer than 30 calendar days (see paragraph (b)(1)(ii) of this section).
(ii) 30 calendar days. When we consider past relevant work and work experience (see § 404.1565), 30 calendar days means a period of 30 consecutive days, including weekends, starting from the first day of work. When we consider whether work lasted 30 calendar days, we generally do not consider the total number of hours or days worked during that period, or whether the work was full-time or part-time. The 30 calendar days requirement is separate from the consideration of substantial gainful activity or whether you worked long enough to learn how to do the work, although the work performed during the 30 calendar days may count toward the time needed for you to learn to do the work. The 30 calendar days requirement also applies if you were self-employed or an independent contractor; we will consider whether you were engaged in the same type of work for 30 calendar days, even if individual work assignments or contracts each lasted fewer than 30 calendar days.
(2) Determining whether you can do your past relevant work. We will ask you for information about work you have done in the past. We may also ask other people who know about your work. (See § 404.1565(b).) We may use the services of vocational experts or vocational specialists, or other resources, such as the “Dictionary of Occupational Titles” and its companion volumes and supplements, published by the Department of Labor, to obtain evidence we need to help us determine whether you can do your past relevant work, given your residual functional capacity. A vocational expert or specialist may offer relevant evidence within his or her expertise or knowledge concerning the physical and mental demands of a claimant's past relevant work, either as the claimant actually performed it or as generally performed in the national economy. Such evidence may be helpful in supplementing or evaluating the accuracy of the claimant's description of his past work. In addition, a vocational expert or specialist may offer expert opinion testimony in response to a hypothetical question about whether a person with the physical and mental limitations imposed by the claimant's medical impairment(s) can meet the demands of the claimant's previous work, either as the claimant actually performed it or as generally performed in the national economy.
(3) If you can do your past relevant work. If we find that you have the residual functional capacity to do your past relevant work, we will determine that you can still do your past work and are not disabled. We will not consider your vocational factors of age, education, and work experience or whether your past relevant work exists in significant numbers in the national economy.
(c) Other work. (1) If we find that your residual functional capacity does not enable you to do any of your past relevant work or if we use the procedures in § 404.1520(h), we will use the same residual functional capacity assessment when we decide if you can adjust to any other work. We will look at your ability to adjust to other work by considering your residual functional capacity and the vocational factors of age, education, and work experience, as appropriate in your case. (See § 404.1520(h) for an exception to this rule.) Any other work (jobs) that you can adjust to must exist in significant numbers in the national economy (either in the region where you live or in several regions in the country).
(2) In order to support a finding that you are not disabled at this fifth step of the sequential evaluation process, we are responsible for providing evidence that demonstrates that other work exists in significant numbers in the national economy that you can do, given your residual functional capacity and vocational factors. We are not responsible for providing additional evidence about your residual functional capacity because we will use the same residual functional capacity assessment that we used to determine if you can do your past relevant work.