According to the IRS, more than 390,000 taxpayers who are entitled to rebates and refunds have not received their checks. 295,000 of those checks are rebates that the IRS issued sometime between July and September, but the checks were returned to the IRS as undeliverable. For the most part, the checks couldn't be delivered because the taxpayer had moved, married, or changed their name.

It's not too late for taxpayers to get their rebates. But the IRS has to process the checks before the end of the year; and that means taxpayers have only until December 5th to request that the checks be reissued. After that date, the rebates can only be claimed on their 2001 tax returns. The average, undelivered rebate check is $322.

The IRS also has 95,500 regular tax refunds that could not be delivered. The average refund is $927.

The IRS says that taxpayers who think they are missing a rebate or a refund check should check their financial records and call their tax preparers. Then, if they think they are missing a check, call IRS toll-free assistance at 1-800-829-1040 to find out how to proceed.