Stopping Improper Payments to Deceased People Act This bill expands and otherwise modifies the sharing of death data, particularly with regard to the recovery of improper payments to deceased individuals. The bill requires the Social Security Administration (SSA) to pay to states their reasonable costs for compiling and sharing records of deaths with the SSA. Under current law, the SSA is not required to pay the states but may choose to do so. In addition, the SSA may share, if certain conditions are met, the death data with federal and state agencies for a broader range of purposes. Such purposes include ensuring proper payments of benefits and tax administration duties. This authority terminates after five years. The Office of Management and Budget shall develop guidance for federal agencies that collect death data, and the Department of the Treasury and the Department of Health and Human Services shall jointly develop a plan to assist and states, local agencies, and Indian tribes in providing the data. Additionally, the SSA must share, within 30 days, death data with Treasury to facilitate the recovery of certain stimulus payments made to individuals who were deceased before January 1, 2020.