retrieved by a taxpayer through _e-sero_ , significantly alleviating the burden of having to store invoices and making it easier to file tax returns. Furthermore, a number of people can logon to _e-sero_ with the same ID and the digital authentication certificate and issue ETIs simultaneously, making it possible for the employees of businesses in different places to issue ETIs anytime and anywhere through _e-sero_ . For those without an access to Internet, telephone ARS similar to telephone banking is available for ETI issuance. ETIs can also be issued through electronic terminals used for credit cards, check cards, and cash receipts. The NTS not only made available a variety of ETI methods to let small businesses issue ETIs without substantial costs, but also helped them reduce the cost of tax accounting and filing tax returns by using _e-sero_ . Large-scale businesses that already have their own information system such as ERP can also issue ETIs through their ERP system after acquiring the standard certification and registering their system to the NTS. Small- and medium-sized companies that issue a large volume of ETIs can outsource ETI issuing to application service providers as well.

In addition to introducing ETI in 2008, the Ministry of Strategy and Finance and the NTS have undertaken a series of measures to lighten the overall tax compliance cost. The notable measures include the release of the “Advanced Interpretation of Tax Legislation” in 2008 to help taxpayers estimate their tax liability in advance, the use of credit cards for the payment of national taxes in 2008, simplified electronic tax return filing for small- and micro-companies in 2009, recognition of electronicallyconverted paper documents in 2009, and “My NTS Service” providing integrated tax information search to taxpayers in 2010. Together with these measures, the NTS announced its goal of cutting tax compliance costs by 15 percent between 2011 and 2016 (the NTS, 2013).

With the variety of supporting measures for taxpayers, the NTS ramped up its capability to combat tax evasions and frauds as well. The NTS launched an ETI early warning system (EWS) to combat invoice seller fraud and identify input tax credit frauds in January 2012 following the internal development from 2009 to 2011.<sup>50</sup> The EWS was developed through identifying fraud types, configuring analysis processes, and structuring early warning typology with series of expert and user consultations and pilot testing in 13 regional tax offices for two months. The EWS provides profiles of suspicious transactions using information from ETIs, corporate income tax filings, tax delinquency records, and other sources to help tax examiners decide on further actions. The EWS is used to not only issue early warnings for tax frauds, but also conduct risk assessment and verify VAT refund claims.

One key function of the EWS is to monitor ETI issuing in real time and produce an alarm when invoice seller fraud is identified even before VAT is filed. The EWS analyzes monthly ETI transactions and taxpayers’ filing information within 15 days

> 50 The NTS developed EWS as one component of ETI systems. Development cost for EWS was approximately KRW700 million (USD630,000) for three years from 2009 to 2011.

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