15. Proof of Payment, Assessment of Tax payable in cases of non-payment or short payment by enrolled persons as well as by persons failing to get enrolled

(1) Subject to the provision of sub-rule (la), a person liable to pay tax shall make payment of the tax in the manner prescribed in rule 12 within the period specified in sub-section (2) of section 8 and shall forward a copy of the receipted challan to the prescribed authority.

(la) Notwithstanding anything contained in sub-rule (1), a person, who is required to make payment of tax under clause (b) of sub-section (4) of section 5, shall make payment of tax in the manner prescribed in sub-rule (2) of rule 12 within the period specified in the said clause and shall attach a copy of the receipted challan with the application for enrolment made under sub-rule (1) of rule 4. 

(2) If it comes to the notice of the prescribed authority that a person enrolled under sub-section (2) of section 5 has failed to pay the amount of tax due from him in the manner laid down in sub-rule (1), he shall serve on that person a notice in Form X requiring him on a date specified in the notice to attend in person or through an authorized representative for showing cause for non-payment of tax. After giving the person a reasonable opportunity of being heard and after holding such enquiry as may be deemed necessary or otherwise if the prescribed authority is satisfied that the tax is payable but it has not been paid, the said authority shall serve a notice of demand in Form XI on that person or his representative to pay the amount within fifteen days from the receipt of the notice. 

(2a) Where the prescribed authority has, upon information received, reasons to believe that any person enrolled under sub-section (2) of section 5 of the Act and specified in column (2) against anyone or more of the entries of the Schedule to the Act, has paid tax at a rate lower than what is payable by such person under the Act, or such person has not paid tax for any year, or has made an application for refund under the proviso to section 18 of the Act, such authority shall serve upon such person a notice in Form XA requiring him to attend, on a date specified in the notice, in person or through an authorized representative, for showing cause for non-payment of tax and against determination of tax under subsection (2) of section 17 A of the Act. After giving such person a reasonable opportunity of being heard and after examining such account or documents or holding such enquiry as may be deemed necessary or otherwise, if the prescribed authority is satisfied that tax has been paid at a rate lower than what is payable or has not been paid at all by such person under the Act, he shall determine such amount of tax as is payable by him under .the Act, and serve a notice of demand in Form XIA on such person to pay the amount due within fifteen days from the receipt of the notice, or grant a refund adjustment order in Form XVIII in accordance with the proviso to section 18 of the Act.

(3) If a person liable to pay tax has failed to get himself enrolled, the prescribed authority shall serve on that person a notice in Form XII requiring him on a date specified in the notice to attend in person or through an authorized representative for showing cause for non-enrolment. After giving the person reasonable opportunity of being heard and after such enquiry as may be deemed fit or otherwise, the prescribed authority .shall assess the tax due to the best of his judgment and serve on him a notice of demand in Form XIII to pay the tax within fifteen days from the receipt of the notice.