The Treasury Department would continue disbursements of Social Security funds, automated revenue collections and the work of daily cash management for the government, in addition to paying interest on the federal debt.

But the Internal Revenue Service, which is Treasury’s largest component, would cease some of its key functions, such as audits, examinations of returns, processing of paper returns and call-center operations for taxpayers with questions.

“It’s going to make it impossible for taxpayers to get the help they need,” National Treasury Employees Union president Colleen M. Kelley said during a conference call with reporters Friday.

Overall, the Treasury Department would place about 88 percent of its 101,000 employees on furlough. That includes about 90 percent of the IRS workforce.

About 8,800 of the IRS’s 95,000 employees would remain at work for “excepted” roles such as law enforcement — considered necessary to protect life and property — or because their positions are paid for by funds outside of congressional appropriations, among other reasons. Most headquarters and administrative employees would be furloughed, according to the agency’s contingency plan.

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