Except as otherwise prescribed by this Act, a business entity, whether or not it has sales, shall file a bimonthly tax return on a prescribed form for its sales amount and tax payable or overpaid of the preceding two months together with tax deduction and other appropriate documents with the competent tax authority prior to the fifteenth day of the following period. The business tax payable, if any, shall be paid to the government treasury in advance. The receipt for tax paid shall be enclosed with the tax return. 
A business entity which applies zero ratings as prescribed in Article 7 of this act may apply to the competent tax authority for filing a monthly tax return for its sales amount and tax payable or overpaid of the preceding month prior to the fifteenth day of the following month. Once approved to file a monthly tax return, the business entity cannot apply for approval to change the filing period within a year. 
The business entities mentioned in the preceding two paragraphs, if using uniform invoices, shall further enclose a detailed list of uniform invoices used.