Got a complex tax problem? Telephoning an IRS Taxpayer Assistance Center for an appointment won't necessarily produce a solution, a federal audit shows.

Eight phone messages seeking help from 50 IRS assistance centers went unreturned, according to an audit by the Treasury Inspector General for Tax Administration.

Five other calls weren't returned within two business days, as IRS guidelines require, auditors found.

And while the centers responded to 27 out of 36 messages about complex tax account problems — the issues that assistance centers are supposed to schedule appointments for — the auditors scheduled only five face-to-face appointments.

That performance undermined the centers' mission, the auditors concluded, noting that "convenience of scheduling appointments could encourage taxpayers to try to resolve tax account problems earlier, thus reducing taxpayer burden."

"When the IRS doesn't provide proper customer service, it's harder for honest taxpayers to pay their taxes correctly," said Carol Guthrie, a spokeswoman for Sen. Max Baucus, D-Mont.

"The IRS has made it clear it would like taxpayers to go to its Web site" for help, said Colleen Kelley, head of the National Treasury Employees Union, which represents Internal Revenue Service workers. "That works for some people, but not for others."

The IRS maintains 400 Taxpayer Assistance Centers nationwide. It encourages taxpayers to request face-to-face appointments for tax account issues that cannot be resolved over the telephone. Designated taxpayer phone lines in the offices got roughly 500,000 calls during the 2006 federal tax season, from January through mid-April, the audit reported.