Money recovery on behalf of deceased person

Whether the property is registered in favour of the Buyer and if so what was exactly mentioned in the Sale Deed regarding purchase consideration and its payment. 

Is there any instrument where the buyer undertook to pay the balance amount in so and so period? Was there any written communication from the buyer stating that he would pay the balance amount with date/period. The original sale was about 7 years back. What action was initiated so far by the deceased person?

Unless all related papers are examined, a proper suggestion cannot be given.

Why Income Tax Department is brought into the matter? Income Tax Department shall not evince interest in such disputes unless there was a reason for them to believe that the payments were not shown on records and thereby tax was evaded.

You may consult a local able and reliable Lawyer with the available papers and seek his/her guidance and act accordingly.

Without the verification of records and communication we cant put our suggestions. better to show all relevant records to local advocate and get  clarity 

Contact a local advocate, issue notice on behalf of his legal heirs, and wait for his reply notice and file a suit for a specific performance suit at the earliest.  Possession and mutation details are most essential for proceeding further as possession determines the extent of the court fee.

If the sale deed was executed by a registered ded, in which there was no clause or condition mentioned that the sale deed would become invalid if the balance of sale consideration amount has not been settled within a stipulated time period thereto, then it was the responsibility for the seller to enforce the same and taken steps to cancel the sale deed for this reason or at least filed a suit for recovery of balance amount.

If the vendor had not initiated any steps towards recovery of the money so far by due process of law, the claim for the said balance amount of sale consideration may be barred by law of limitation at this stage.

Hence you may revert with the details besides the details sought by the other experts above in this regard so that a proper opinion and useful suggestions can be rendered, provided you are really serious about the issue and are desirous of solution to the problem. 

Yes, what is the condition in the sale deed as to payment of the outstanding amount?