(a) Annual audit--Except as provided in subsection (c) of this section, the board of directors or trustees shall at least once each year have made, by certified public accountants selected by the institution and satisfactory to the department, an audit of the books and affairs of the institution including such matters as may be required by the department and including, in the case of a bank and trust company, a savings bank or a trust company, accounts held in a fiduciary or other representative capacity. The department may by regulation establish minimum standards for audits and reports under this subsection (a).

(b) Audit report--A report of the audit made under subsection (a) of this section shall be signed by the certified public accountants who make it and filed with the department and a signed copy of the report shall be submitted to the board and kept in the files of the institution.

(c) Internal auditors--In the case of an institution which has a system of internal audit control approved by the department, no audit under subsection (a) of this section shall be required and in lieu of the report required by subsection (b), the auditor or comptroller of the institution shall submit to the board an annual summary report of the same matters as those required under subsection (a) of this section. Such report shall set forth the degree of compliance with the approved audit system and shall express the opinion of the auditor or comptroller as to the adequacy of the internal controls. The report shall be kept in the files of the institution and a copy shall be filed with the department.

(d) Accounting standards--Audits and reports shall be deemed to satisfy the requirements of this section to the extent the audits and reports conform to accounting standards and principles applicable pursuant to 12 U.S.C. § 1831n to reports or statements required to be filed with Federal banking agencies.