Financial authorities will start requiring private educational institutes and postnatal care centers to issue cash receipts next month as part of efforts by the Park Geun-hye administration to broaden the revenue base, industry sources said Friday. According to the sources, real estate brokers and funeral services will also have to start issuing cash receipts on Oct. 1. The new measure, which was collectively agreed upon by the National Tax Service (NTS) and the nation\'s finance ministry and related agencies, is part of President Park\'s campaign pledge to discover hidden revenue from establishments that have previously shunned credit card transactions to avoid taxes. The government has so far failed to track the cash revenue of these businesses, but their rapid growth has made them an untapped tax gold mine. These establishments must register with the NTS as so-called cash receipt member stores and set up devices to print out the type of receipts that customers can use when filing income tax for deductions. The cash receipt system in South Korea was first adopted in 2005 to offer tax deductions to workers whose cash expenditures exceed 25 percent of their private income. The tax benefits may be applied to 20 percent of these expenditures but cannot exceed 3 million won (US$2,742).