When a business entity, whose business tax is assessed as prescribed in Article 23, purchases goods or services for business operation, obtains evidence stating amount of pertinent business tax, and files a return as required, 10% of input tax shall be deducted from the assessed tax amount by the competent tax authority. However, when the assessed tax amount is less than the minimum amount for assessment, this deduction shall not be applicable. 
If, as provided in the preceding paragraph, 10% of input tax exceeds the assessed tax amount, the excess may be deductible in the coming period.