20 CFR § 404.507 - Fault.
Fault as used in without fault (see § 404.506 and 42 CFR 405.355) applies only to the individual. Although the Administration may have been at fault in making the overpayment, that fact does not relieve the overpaid individual or any other individual from whom the Administration seeks to recover the overpayment from liability for repayment if such individual is not without fault. In determining whether an individual is at fault, the Social Security Administration will consider all pertinent circumstances, including the individual's age and intelligence, and any physical, mental, educational, or linguistic limitations (including any lack of facility with the English language) the individual has. What constitutes fault (except for deduction overpayments - see § 404.510) on the part of the overpaid individual or on the part of any other individual from whom the Administration seeks to recover the overpayment depends upon whether the facts show that the incorrect payment to the individual or to a provider of services or other person, or an incorrect payment made under section 1814(e) of the Act, resulted from:
(a) An incorrect statement made by the individual which he knew or should have known to be incorrect; or
(b) Failure to furnish information which he knew or should have known to be material; or
(c) With respect to the overpaid individual only, acceptance of a payment which he either knew or could have been expected to know was incorrect.