20 CFR § 404.304 - What are the general rules on benefit amounts?
This subpart describes how we determine the highest monthly benefit amount you ordinarily could qualify for under each type of benefit. However, the highest monthly benefit amount you could qualify for may not be the amount you will be paid. In a particular month, your benefit amount may be reduced or not paid at all. Under some circumstances, your benefit amount may be increased. The most common reasons for a change in your benefit amount are listed below.
(a) Age. Sections 404.410 through 404.413 explain how your old-age, wife's or husband's, or widow's or widower's benefits may be reduced if you choose to receive them before you attain full retirement age (as defined in § 404.409).
(c) Overpayments and underpayments. Your benefits may be increased or decreased to make up for any previous overpayment or underpayment made on the insured person's record. For more information about this, see subpart F of this part.
(d) Family maximum. Sections 404.403 through 404.406 explain that there is a maximum amount payable on each insured person's earnings record. If you are entitled to benefits as the insured's dependent or survivor, your benefits may be reduced to keep total benefits payable to the insured's family within these limits.
(e) Government pension offset. If you are entitled to wife's, husband's, widow's, widower's, mother's, or father's benefits and receive a Government pension for work that was not covered under Social Security, your monthly benefits may be reduced because of that pension. For more information about this, see § 404.408a, which covers reductions for Government pensions.
(f) Rounding. After all other deductions or reductions, we reduce any monthly benefit that is not a multiple of $1 to the next lower multiple of $1.