SSI/SSP. The monthly SSI payment made by the SSA to beneficiaries, which combines both Federal SSI program funds and SSP funds. SSI/SSP Transfer Date: The dollar-weighted average day of clearance of the regularly issued monthly SSI/SSP checks issued by the SSA, adjusted to reflect three payment variations. Due Date: The day on which States are required to deposit funds to the SSA. Deposit Date: The day on which State funds are deposited to the SSA.