Equal Treatment of Public Servants Act of 2021 This bill phases in a new funding formula for determining benefit amounts under the windfall elimination provision (WEP). The WEP reduces Social Security retirement and disability benefits for those who receive pensions for certain non-covered employment. The new formula adjusts an individual's total lifetime earnings based on the proportion of those earnings subject to Social Security payroll taxes. It applies to individuals who (1) become eligible for Social Security benefits after 2061, and (2) have earnings from non-covered service performed in a year after 1977. Beneficiaries who become eligible for benefits between 2023 and 2061 receive the higher of their benefit calculated under the existing WEP or the new formula. In addition, certain beneficiaries currently impacted by the WEP receive an additional payment. The Social Security Administration must include non-covered earnings in Social Security account statements and must study the feasibility of partnering with certain pension systems to address data sharing issues related to non-covered pensions.