The Internal Revenue Service (IRS) recently posted its contingency plan for managing operations during the federal government shutdown, which includes reducing its available workforce for IRS functions by over 87 percent. Employees may be kept on for half a day to ensure an orderly close-down of operations. After the half-day period, most IRS activities will cease, including the issuing of refunds, processing amended returns, responding to taxpayer phone calls, and providing legal counsel. All audit functions will also stop during the shutdown period.
For further details, you can read the IRS contingency plan here [PDF].