Previous year tax liability

My group had a Mumbai based company which was sold off in Jan 2012. The company never acquired 
professional tax regn and hence never paid any professional tax. Now, after 1.5 years of sale, 
the group has received an email containing the notice from the Dept of Maharashtra for payment 
of the same for the previous 8 years. Though I think that the group is liable since it was the 
conducting the operatons the business during the period of defualt, but still confused a bit. 
Could you please clarify whether the group or the purchaser is liable for the payment of  
professional tax?

Thanks!