The opinion of the court was delivered by: Jean P. Rosenbluth U.S. Magistrate Judge
DECISION AND REMANDING MEMORANDUM OPINION AND ORDER REVERSING COMMISSIONER'S FOR FURTHER PROCEEDINGS
Plaintiff seeks review of the Commissioner's final decision denying her application for Social Security Disability Insurance Benefits ("DIB"). The parties filed a Joint Stipulation on January 3, 2012.*fn1 The Court has taken the Joint Stipulation under submission without oral argument. For the reasons stated below, the Commissioner's decision is reversed and this matter is remanded for further proceedings.
Plaintiff was born on August 14, 1953. (Administrative Record ("AR") 33, 106.) She completed high school in El Salvador and speaks limited English. (AR 24, 33-34.) Plaintiff came to the United States in 1974 and worked as a sample maker at a sewing factory until January 1, 2002. (AR 33-34.) She has not engaged in substantial gainful activity from that date through her date last insured, March 31, 2006. (AR 34, 106.)
On March 31, 2008, Plaintiff filed an application for DIB, alleging that she had been unable to work since January 1, 2002, because of several medical problems, including foot pain, knee pain, lumbar spine disorder, rheumatoid arthritis, and fibromyalgia. (AR 17, 19, 106.) After Plaintiff's application was denied, she requested a hearing before an Administrative Law Judge ("ALJ"). (AR 58.) It was held on September 17, 2009, at which time Plaintiff appeared with a representative and testified on her own behalf. (AR 29-47.) Two medical experts and a vocational expert also testified. (AR 38-46.) On November 2, 2009, the ALJ found that Plaintiff was not disabled within the meaning of the Social Security Act. (AR 17-25.) On January 26, 2011, the Appeals Council denied Plaintiff's request for review of the ALJ's decision. (AR 1-3.) This action followed.
Pursuant to 42 U.S.C. § 405(g), a district court may review the Commissioner's decision to deny benefits. The Commissioner's or ALJ's findings and decision should be upheld if they are free of legal error and are supported by substantial evidence based on the record as a whole. § 405(g); Richardson v. Perales, 402 U.S. 389, 401, 91 S. Ct. 1420, 1427, 28 L. Ed. 2d 842 (1971); Parra v. Astrue, 481 F.3d 742, 746 (9th Cir. 2007). Substantial evidence means such evidence as a reasonable person might accept as adequate to support a conclusion. Richardson, 402 U.S. at 401; Lingenfelter v. Astrue, 504 F.3d 1028, 1035 (9th Cir. 2007). It is more than a scintilla but less than a preponderance. Lingenfelter, 504 F.3d at 1035 (citing Robbins v. Soc. Sec. Admin., 466 F.3d 880, 882 (9th Cir. 2006)). To determine whether substantial evidence supports a finding, the reviewing court "must review the administrative record as a whole, weighing both the evidence that supports and the evidence that detracts from the Commissioner's conclusion." Reddick v. Chater, 157 F.3d 715, 720 (9th Cir. 1996). "If the evidence can reasonably support either affirming or reversing," the reviewing court "may not substitute its judgment" for that of the Commissioner. Id. at 720-21.
IV. THE EVALUATION OF DISABILITY
People are "disabled" for purposes of receiving Social Security benefits if they are unable to engage in any substantial gainful activity due to a physical or mental impairment that is expected to result in death or which has lasted, or is expected to last, for a continuous period of at least 12 months. 42 U.S.C. § 423(d)(1)(A); Drouin v. Sullivan, 966 F.2d 1255, 1257 (9th Cir. 1992).
A. The five-step evaluation process The Commissioner (or ALJ) follows a five-step sequential evaluation process in assessing whether a claimant is disabled. 20 C.F.R. § 404.1520(a)(4); Lester v. Chater, 81 F.3d 821, 828 n.5 (9th Cir. 1995) (as amended Apr. 9, 1996). In the first step, the Commissioner must determine whether the claimant is currently engaged in substantial gainful activity; if so, the claimant is not disabled and the claim is denied. § 404.1520(a)(4)(I). If the claimant is not engaged in substantial gainful activity, the second step requires the Commissioner to determine whether the claimant has a "severe" impairment or combination of impairments significantly limiting her ability to do basic work activities; if not, a finding of non-disability is made and the claim is denied. § 404.1520(a)(4)(ii). If the claimant has a "severe" impairment or combination of impairments, the third step requires the Commissioner to determine whether the impairment or combination of impairments meets or equals an impairment in the Listing of Impairments ("Listing") set forth at 20 C.F.R. Part 404, Subpart P, Appendix 1; if so, disability is established and benefits are awarded. § 404.1520(a)(4)(iii). If the claimant's impairment or combination of impairments does not meet or equal an impairment in the Listing, the fourth step requires the Commissioner to determine whether the claimant has sufficient residual functional capacity ("RFC")*fn2 to perform her past work; if so, the claimant is not disabled and the claim must be denied. § 404.1520(a)(4)(iv). The claimant has the burden of proving that she is unable to perform past relevant work. Drouin, 966 F.2d at 1257. If the claimant meets that burden, a prima facie case of disability is established. Id. If that happens or if the claimant has no past relevant work, the Commissioner then bears the burden of establishing that the claimant is not disabled because she can perform other substantial gainful work in the economy. § 404.1520(a)(4)(v). That determination comprises the fifth and final step in the sequential analysis. § 404.1520(a)(4)(v); Lester, 81 F.3d at 828 n.5; Drouin, 966 F.2d at 1257.
B. The ALJ's application of the five-step process At step one, the ALJ found that Plaintiff did not engage in any substantial gainful activity from January 1, 2002, the date of the onset of her alleged disability, through March 31, 2006, her date last insured. (AR 19.) At step two, the ALJ concluded that Plaintiff had the severe impairments of "foot pain; knee pain; lumbar spine disorder; rheumatoid arthritis and fibromyalgia." (Id.)
At step three, the ALJ determined that Plaintiff's impairments did not meet or equal any of the impairments in the Listing. (AR 21.) At step four, the ALJ found that through the date last insured, Plaintiff had the RFC to perform a limited range of "light work";*fn3 specifically, she could "lift and carry up to 20 pounds occasionally and 10 pounds frequently; stand and walk up to 4 hours in an 8 hour day;  sit for up to 6 hours in an 8 hour day; . . . occasionally climb ladders, ropes, and scaffolds; occasionally climb ramps and stairs; and occasionally bend, stoop, or squat." (Id.); see 20 C.F.R. § 404.1567(b). The ALJ concluded that Plaintiff was unable to perform her past relevant work as a sample maker but acquired from that work transferable sewing skills. (AR 23-24.)
At step five, the ALJ found, based on the VE's testimony and application of the Medical--Vocational Guidelines, that jobs existed in significant numbers in the national economy that Plaintiff could perform. (AR 24-25.) The ALJ agreed with the VE that Plaintiff could perform the work of "sewing machine operator." ...