The IRS has some bad news for some 30,000 taxpayers in 13 states.

These unlucky check writers didn't forget to pay their taxes, and they didn't make a mistake on their returns. But they might want to start looking for their checkbooks -- because the payments they made on their estimated taxes due last week are now most likely at the bottom of the San Francisco Bay.

The checks were lost early on the morning of Sept. 11, when the truck that was transporting them to an IRS lockbox got in an accident on the San Mateo Bridge, and 30,000 pieces of mail were blown all around, including into the bay.

``We believe these are almost all estimated tax payments that were due on Sept. 15,'' said Terry Lemons, an IRS spokesman in Washington.

Lemons said the agency will happily waive penalties and interest for anyone whose payment was lost, and it is asking people who sent mail to the PO Box 510000 in San Francisco during the first 10 days of the September to sit tight and see if their checks clear.

``We are asking people's patience during this period,'' Lemons said. ``The key thing we are going to do is work to make it as easy as possible for taxpayers.''

Lemons said the mishap could potentially affect taxpayers in California, Alaska, Arizona, Hawaii, Idaho, Montana, Nevada, Ohio, Oregon, Utah, Virginia, Washington and Wyoming.

``I've driven back and forth between home and office, thinking . . . what a mess,'' said Kim Kastl, a Hayward tax specialist who calculates that half of her 600 clients may -- or may not -- be affected.