Section 11D(1) in Punjab General Sales Tax Act, 1948
(1)If any dealer fails to pay the amount of tax due from him as required by sub-section (4) of section 10, he shall, in addition to the amount of tax, be liable to pay simple interest on the amount of tax due from him at the rate of one per centum per month from the date immediately following the last date for the submission of the return under sub-section (3) of that section, for a period of one month and thereafter at the rate of [two per centum] per month till the default continues.