Regarding the application for reduced tax rates on domestic source income for non-resident individuals, the relevant form is the "Application for Application of Reduced Tax Rate" (시행규칙 별지 제29호의 12 서식). This form is submitted to the withholding agent before receiving the domestic source income.
If the domestic source income is received indirectly through a foreign investment vehicle, the foreign investment vehicle must submit the "Foreign Investment Vehicle Report" (시행규칙 별지 제29호의 13 서식) along with the details of the beneficial owner to the withholding agent before receiving the domestic source income.
These forms are based on the Income Tax Act (소득세법) and its Enforcement Decree and Regulations.