The Internal Revenue Service, which is responsible for collecting federal taxes and enforcing federal tax law, was unable to accurately deal with its own complex rules governing the payment of its own employees and ended up overpaying more than 600 IRS workers about $4,200,000, according to an audit report by the Treasury Inspector General for Tax Administration. The IRS also underpaid more than 900 employees about $2,700,000, according to TIGTA’s estimate. The inspector general found that the IRS’s rules for how it determines the correct pay for one of its own employees when he or she is promoted to a...