Fake purchase bill in 1996

Hello,

A partnership firm named say 'XYZ Enterprises' did a fake purchase transaction of Rs.10 lac way back in 1996. In reality there was no deal. It was just cheque given and cash taken. Now Income Tax Department has come to know of this and the Partners of the firm have agreed to it. Is there in any way the Partnership Firm can be be levied any penalty/interest? If yes, under which section? Whether this will be 'Concealment u/s 271(1)(c)' or whether this will be 'Income Escaping Assessment? What will be the amount of penalty/interest?

I believe this transaction is time-barred and there is nothing Income Tax Department can do about this. Is this true?