                  FOR PUBLICATION
  UNITED STATES COURT OF APPEALS
       FOR THE NINTH CIRCUIT

CYNTHIA D. CARRILLO-YERAS,              
                 Plaintiff-Appellant,         No. 09-56515
                 v.
                                                D.C. No.
                                            2:08-cv-05560-AN
MICHAEL J. ASTRUE, Commissioner
of Social Security,                             OPINION
               Defendant-Appellee.
                                        
       Appeal from the United States District Court
           for the Central District of California
       Arthur Nakazato, Magistrate Judge, Presiding

                  Argued and Submitted
           August 30, 2011—Pasadena, California

                   Filed October 25, 2011

 Before: Arthur L. Alarcón, Diarmuid F. O’Scannlain, and
            Barry G. Silverman, Circuit Judges.

                Opinion by Judge Silverman




                            19493
                  CARRILLO-YERAS v. ASTRUE             19495




                        COUNSEL

Lawrence D. Rohlfing, Santa Fe Springs, California, for the
plaintiff-appellant.

Scott J. Borrowman, Social Security Administration, Office of
General Counsel, San Francisco, California, for the
defendant-appellee.
19496             CARRILLO-YERAS v. ASTRUE
                           OPINION

SILVERMAN, Circuit Judge:

   Cynthia Carillo-Yeras appeals the district court’s decision
affirming the Social Security Administration’s denial of her
applications for disability insurance benefits and supplemental
security income. Because the SSA took nearly two years to
investigate whether to reopen a favorable determination on
one of Carillo-Yeras’s applications, much longer than the pre-
sumptive time of six months, 20 C.F.R. §§ 404.991a(a),
416.1491(a), and because the record does not show that the
investigation was “diligently pursued,” id., we reverse.

                      I.   Background

   In 1996, Carillo-Yeras fell and fractured her coccyx. The
fracture did not heal properly and she underwent surgery to
remove a fragment of the bone. She continued to suffer from
low back pain after the surgery, which worsened following
the birth of her son in 1999. Carillo-Yeras’s doctors treated
the pain with prescription painkillers and a muscle relaxant.
She received a series of epidural steroid injections and under-
went a brief course of physical therapy. In July 2001, after
these treatments failed to eliminate her pain, Carillo-Yeras
had another surgery. The surgery, a bilateral laminotomy-
foraminotomy, appeared to help relieve Carillo-Yeras’s symp-
toms, and she received only intermittent, conservative treat-
ment until 2005. In 2005 and 2006, she sought regular
treatment and received additional epidural steroid injections
and facet blocks.

   On May 25, 2000, Carillo-Yeras applied for disability
insurance benefits, alleging disability due to low back pain
beginning in July 1999. After Carillo-Yeras’s application was
denied initially and on reconsideration, she requested a hear-
ing before an Administrative Law Judge. On March 24, 2003,
after a hearing, the ALJ denied Carillo-Yeras’s application,
                   CARRILLO-YERAS v. ASTRUE               19497
finding that she had the residual functional capacity to per-
form her past work as a medical receptionist or hospital
admitting clerk. Carillo-Yeras sought Appeals Council review
of the decision.

   On June 20, 2003, while her request for Appeals Council
review of the ALJ’s unfavorable decision was pending,
Carillo-Yeras filed a second application for disability insur-
ance benefits and for supplemental security income. This
time, she alleged disability beginning March 25, 2003 due to
back injury, numbness and tingling with a burning sensation,
and a diagnosis of arachnoiditis. On August 19, 2003, the
state agency responsible for the initial determination of dis-
ability found that Carillo-Yeras met the criteria of the medical
listing for spinal arachnoiditis. As a result, the agency con-
cluded that Carillo-Yeras was disabled as of March 25, 2003.
She began receiving disability insurance benefits and supple-
mental security income.

   On June 2, 2004, the Appeals Council granted Carillo-
Yeras’s request for review of the March 24, 2003 denial of
her first application. It also reopened the August 19, 2003
favorable determination on her second application. The
Appeals Council notified Carillo-Yeras of its intent to consol-
idate the two cases and remand for a new hearing. After
receiving no comments from Carillo-Yeras on its proposed
course of action, the Appeals Council remanded the cases on
September 15, 2004.

   On May 16, 2006, after receiving additional medical
records and conducting a supplemental hearing, the ALJ
issued a new decision denying both of Carillo-Yeras’s appli-
cations for benefits. The ALJ made no mention of the 23-
month delay between the time the case was reopened and the
new decision rendered, nor did he make any finding that the
SSA had been diligent in pursuing the investigation of the
matter. He found that the record did not support a diagnosis
of spinal arachnoiditis and concluded that Carillo-Yeras was
19498              CARRILLO-YERAS v. ASTRUE
not disabled because she had the residual functional capacity
to perform her past relevant work. Carillo-Yeras sought
Appeals Council review of the unfavorable decision, and the
Council denied her request.

   Carillo-Yeras then filed a complaint in district court, argu-
ing that the applicable regulations prohibited the ALJ from
revising the August 19, 2003 favorable determination without
first finding that the agency diligently pursued its investiga-
tion into whether it should revise, and that the ALJ erred in
rejecting the opinion of Carillo-Yeras’s treating physicians
and in finding her subjective symptom testimony to be “not
entirely credible.” The district court affirmed the ALJ’s denial
of benefits, and Carillo-Yeras appeals. We have jurisdiction
under 28 U.S.C. § 1291.

                        II.   Discussion

A.   Standard of Review

   We review de novo the district court’s order upholding the
ALJ’s denial of benefits. Moisa v. Barnhart, 367 F.3d 882,
885 (9th Cir. 2004). We may overturn the ALJ’s decision
“only if it is not supported by substantial evidence or if it is
based on legal error.” Thomas v. Barnhart, 278 F.3d 947, 954
(9th Cir. 2002) (quotation marks and citation omitted).

B.   Timeliness of Revision

   The SSA may reopen a determination regarding eligibility
for disability insurance benefits (a) “[w]ithin 12 months of the
date of the notice of the initial determination, for any reason;”
(b) “[w]ithin four years of the date of the notice of the initial
determination if [the agency] find[s] good cause, as defined
in § 404.989, to reopen the case;” or (c) “[a]t any time,” if the
determination was obtained by fraud or in certain other speci-
fied circumstances. 20 C.F.R. § 404.988. Similarly, a determi-
nation regarding eligibility for supplemental security income
                  CARRILLO-YERAS v. ASTRUE               19499
may be reopened (a) “[w]ithin 12 months of the date of the
notice of the initial determination, for any reason;” (b)
“[w]ithin two years of the date of the notice of the initial
determination if [the agency] find[s] good cause, as defined
in § 416.1489, to reopen the case;” or (c) “[a]t any time if it
was obtained by fraud or similar fault.” 20 C.F.R. § 416.1488.

   In certain circumstances, the SSA may revise a determina-
tion after the expiration of the time limits in 20 C.F.R.
§§ 404.988 and 416.1488:

       We may revise a determination or decision after
    the applicable time period in § 404.988(a) [or
    § 416.1488(a)] or § 404.988(b) [or § 416.1488(b)]
    expires if we begin an investigation into whether to
    revise the determination or decision before the appli-
    cable time period expires. We may begin the investi-
    gation either based on a request by you or by an
    action on our part. The investigation is a process of
    gathering facts after a determination or decision has
    been reopened to determine if a revision of the deter-
    mination or decision is applicable.

       (a) If we have diligently pursued the investigation
    to its conclusion, we may revise the determination or
    decision. The revision may be favorable or unfavor-
    able to you. “Diligently pursued” means that in light
    of the facts and circumstances of a particular case,
    the necessary action was undertaken and carried out
    as promptly as the circumstances permitted. Diligent
    pursuit will be presumed to have been met if we con-
    clude the investigation and if necessary, revise the
    determination or decision within 6 months from the
    date we began the investigation.

       (b) If we have not diligently pursued the investiga-
    tion to its conclusion, we will revise the determina-
    tion or decision if a revision is applicable and if it
19500                CARRILLO-YERAS v. ASTRUE
      will be favorable to you. We will not revise the
      determination or decision if it will be unfavorable to
      you.

20 C.F.R. §§ 404.991a, 416.1491.

   Carillo-Yeras argues that the SSA impermissibly revised
the August 19, 2003 favorable determination because it did
not diligently pursue the revision. Carillo-Yeras’s argument is
primarily based on language found in the SSA’s Program
Operations Manual System (“POMS”), an internal agency
document used by employees to process claims.1 POMS DI
27505.005C, which applies to disability insurance claims,
states: “If the investigation and revision take longer than 6
months, SSA must show that the issue was diligently pur-
sued.” See also POMS GN 04001.060B.1.b (“If the investiga-
tion takes more than 6 months, then SSA will have to show
that it was diligently pursued if the revision would be unfa-
vorable to the individual.”). Carillo-Yeras argues that these
sub-regulatory provisions impose on the ALJ a burden of
making an explicit showing of diligence.

   POMS may be “entitled to respect” under Skidmore v. Swift
& Co., 323 U.S. 134 (1994), to the extent it provides a persua-
sive interpretation of an ambiguous regulation, see Christen-
sen v. Harris Cnty., 529 U.S. 576, 587-88 (2000), but it “does
not impose judicially enforceable duties on either this court or
the ALJ.” Lockwood v. Comm’r Soc. Sec. Admin., 616 F.3d
1068, 1073 (9th Cir. 2010) (citing Lowry v. Barnhart, 329
F.3d 1019, 1023 (9th Cir. 2003)) (holding that ALJ was not
required to explain decision to use claimant’s actual age for
  1
   Carillo-Yeras also cites two sections of the SSA Office of Disability
Adjudication and Review’s Hearings, Appeals and Litigation Law Manual
(“HALLEX”) in support of her argument. But those sections merely para-
phrase the regulations without adding any content, so we do not discuss
them here. Compare HALLEX I-2-9-50, and HALLEX I-3-9-5, with 20
C.F.R. §§ 404.991a, and 416.1491.
                   CARRILLO-YERAS v. ASTRUE                19501
purposes of determining whether claimant could work, where
regulation only required ALJ to consider using older age cate-
gory); see also Moore v. Apfel, 216 F.3d 864, 868-69 (9th Cir.
2000) (declining to review allegations of noncompliance with
internal agency manual because such a manual “does not
carry the force and effect of law.”). For that reason, we
decline to hold that the ALJ erred simply by failing to make
an explicit finding of diligence.

   [1] Nevertheless, even though POMS does not impose any
judicially enforceable duties on the SSA, “[t]he Code of Fed-
eral Regulations is clearly binding upon the Commissioner.”
Moore, 216 F.3d at 869. The regulations applicable here do
not require the ALJ to make an explicit finding of diligent
pursuit or to explain or analyze any periods of delay in the
investigation. See 20 C.F.R. §§ 404.991a, 416.1491. But they
do prohibit the SSA from revising a determination in a man-
ner unfavorable to the claimant after the expiration of the time
limits in 20 C.F.R. §§ 404.988 and 416.1488 if the agency
“ha[s] not diligently pursued the investigation to its conclu-
sion.” 20 C.F.R. §§ 404.991a(b), 416.1491(b). The regula-
tions define “diligently pursued” to mean that “in light of the
facts and circumstances of a particular case, the necessary
action was undertaken and carried out as promptly as the cir-
cumstances permitted.” 20 C.F.R. §§ 404.991a(a),
416.1491(a). Where, as here, a determination is not revised
within six months of reopening, there is no presumption that
the agency diligently pursued its investigation. Id.

   [2] In the absence of any explicit finding of diligence by
the ALJ, we examine the record ourselves to see if it supports
an implicit finding of diligence. The record does not support
a finding that “in light of the facts and circumstances of a par-
ticular case, the necessary action was undertaken and carried
out as promptly as the circumstances permitted.” 20 C.F.R.
§§ 404.991a(a), 416.1491(a). The Appeals Council reopened
the determination on June 2, 2004, and the ALJ did not revise
the determination until May 16, 2006. The record reveals a
19502             CARRILLO-YERAS v. ASTRUE
number of inexplicable delays within this 23-month period,
including more than three months between the Appeals Coun-
cil’s decision to reopen the determination and the order
remanding the consolidated cases to the ALJ; more than three
months between the remand order and any action by the
Office of Hearings and Appeals to begin preparing Carillo-
Yeras’s file for review; four months between the ALJ-ordered
orthopedic consultative examination and the neurologic con-
sultative examination; and more than four months between the
last consultative examination and the notice scheduling the
supplemental hearing.

   [3] Having reviewed the administrative record, we can
deduce no reason for these delays. The ALJ’s decision pro-
vides no explanation. Because the record does not support a
conclusion that the investigation was carried out as promptly
as circumstances permitted, the ALJ lacked authority under
the regulations to revise the August 19, 2003 determination in
a manner unfavorable to Carillo-Yeras. We reverse and
remand with instructions to reinstate the August 19, 2003
determination. See Swensen v. Sullivan, 876 F.2d 683, 689
(9th Cir. 1989) (“We may direct the award of benefits where
no useful purpose would be served by further administrative
proceedings and the record has been thoroughly developed.”).

  REVERSED and REMANDED.
