(1) Only when an entrepreneur falls under any of the following, the head of the tax office or the commissioner of a regional tax office having jurisdiction over the place of tax payment or the Commissioner of the National Tax Service (hereafter in this Article referred to as the "head of the tax office having jurisdiction over the place of tax payment, etc.") shall conduct investigations to decide or rectify the tax base and the amount of tax payable or the amount of tax refundable for value-added tax in the relevant preliminary return period and taxable period:
1. Where he or she fails to file the preliminary return or final return;
2. Where there are any errors or omissions in details of the preliminary return or final return;
3. Where, in filing the final return, he or she fails to submit a sum table of tax invoices by customer or by seller, or where he or she omits or misrepresents all or some of the items to be entered in the sum table of tax invoices by customer or by seller;
4. Where he or she is likely to evade value-added tax on the grounds prescribed by Presidential Decree.
(2) In deciding or rectifying the tax base and the amount of tax payable or the amount of tax refundable for each preliminary return period and taxable period through an investigation under paragraph (1), the head of the tax office having jurisdiction over the place of tax payment, etc. shall do so on the basis of tax invoices, import tax invoices, account books, and other evidentiary materials: Provided, That in any of the following cases, an estimation may be made as prescribed by Presidential Decree:
1. Where tax invoices, import tax invoices, account books, or other evidentiary materials necessary for calculating the tax base are either missing or incomplete in material particulars;
2. Where details of tax invoices, import tax invoices, account books, or other evidentiary materials are obviously false in view of the capacity of facilities, the number of employees, and the market prices of raw materials, commodities, products, or various charges;
3. Where details of tax invoices, import tax invoices, account books, or other evidentiary materials are obviously false in view of the quantity of raw materials used, the amount of electric power used, and other operating situations.
(3) Where any error or omission is found in the tax base, the amount of tax payable, or the amount of tax refundable that is decided or rectified under paragraphs (1) and (2), the head of the tax office having jurisdiction over the place of tax payment, etc. shall immediately re-rectify such error or omission.