HomeTax (홈택스) is the Korean National Tax Service’s (NTS) online portal designed to streamline and digitize tax-related tasks for individuals, businesses, and tax professionals. It allows users to perform a wide range of tax functions without visiting a tax office.

VAT report for business with sales or purchase (매출·매입있는) - at the National Tax Service, on the Hometax website.

Even without sales or purchases (매출·매입없는), you have to make a report every trimester on the website of Hometax or in person at the Tax offic

If you started a business in Korea you are supposed to pay the taxes, as well as if you work in Korea.