Can the person chargeable with tax pay the amount of demand along with interest and reduced penalty before the service of show cause notice under section 74(1) or as the case may be, the statement under section 74(3)

Yes. The person chargeable with tax can pay the amount of tax along with interest under section 50 and a penalty equivalent to 15% of such tax based on his own ascertainment of such tax or the tax as ascertained by the proper officer and inform the proper officer in writing of such payment. in Form GST DRC-03. On receipt of such information, the proper officer shall issue an acknowledgement for accepting the payment made by the said person in Form GST DRC-04 and he shall not serve any notice in respect of tax so paid or any penalty payable under the provisions of this Act or rules made there under.

(ICAI FAQ PUBLICATIONS 06-09-2017 Determination of tax not paid or short paid or erroneously refunded or input tax credit wrongly availed or utilized by reason of fraud or any willful misstatement or suppression of facts: FAQ NO. 12)