The Treasury Department and the Internal Revenue Service announced in late October that business taxpayers may redesignate estimated income tax overpayments as employment tax deposits. The flexibility, intended to help businesses in the aftermath of Sept. 11, will improve cash flow, the department and agency said. The action addresses the situation where taxpayers have already paid estimated tax payments that exceed their tax liability. This might occur, for example, if projected income dropped sharply as a result of the terrorist attacks. To redesignate overpayments, call the IRS’s toll-free disaster relief hotline at (866) 562-5227.