"$250 Social Security Payment and Working Credit: I also received some questions regarding whether this payment would be available to otherwise qualified retirees or disabled people who are also social security recipients. The answer is that it will, but in a reduced fashion. Because there is another provision in the overall stimulus bill of a one-time payment of $250 in 2009 to retirees and disabled people receiving Social Security benefits, the $400 income-tax credit (rebate) will be reduced by $250. To clarify: You get the $250 SS credit (which will distributed as an additional payment) plus a reduced $150 working tax credit (total is still $400).
Update to $250 SSI payment: The Social Security Administration (SSA) reports that everyone who is entitled to the $250 payment should receive it by late May 2009. No action is required on your part. They are currently working on the details regarding it will be issued to nearly 55 million beneficiaries. Note: The Making working Pay $400/$800 credit is being paid by the IRS, while the $250 social security payment is being paid out by the SSA."
I first got this information on somebody's blog. I'd love to give them credit, but I don't remember whose blog it was.