Mr X was having a proprietary firm. He demised on 10-06-2010. He was having only 1 employee whose salary exceeds 5000. Others were having less than 5000. In Dec 2012 a notice from sales tax department received at his office address asking for professional tax with interest and penalty from 01.04.04-31.03.12. Now my query is his legal heirs are liable for all the dues? And books of accounts of Mr X are not available for checking.