Latest amount & definition
The "old-law" contribution and benefit base for 2025 is $130,800. This is the base that would have been effective without the enactment of the 1977 amendments to the Social Security Act. The present-law contribution and benefit base is substantially higher than the old-law base.

Purpose of the old-law base
The old-law contribution and benefit base is used by:

• the Railroad Retirement program to determine certain tax liabilities and tier II benefits payable under that program to supplement the tier I payments which correspond to basic Social Security benefits,
• the Pension Benefit Guaranty Corporation to determine the maximum amount of pension guaranteed for single-employer plans under the Employee Retirement Income Security Act,
• Social Security to determine a year of coverage in computing the special minimum benefit, and
• Social Security to determine a year of coverage (acquired whenever earnings equal or exceed 25 percent of the old-law base for this purpose only) in computing benefits for persons who are also eligible to receive pensions based on non-covered employment.

Determination of the old-law contribution and benefit base for 2025
The formula for determining the old-law contribution and benefit base is set by law. The formula is applicable only if a cost-of-living increase becomes effective for December of the year in which a determination of the base would ordinarily be made. Because there is a cost-of-living increase for December 2024, the formula is applicable. According to the formula, the old-law contribution and benefit base for 2025 is determined to be the 1994 old-law base ($45,000) multiplied by the ratio of the national average wage index for 2023 to that for 1992, or, if larger, the 2024 old-law base ($125,100). If the amount so determined is not a multiple of $300, it is rounded to the nearest multiple of $300.