how to allocate joint property tax in individual account

Sale of immovable property attracts Capital Gain Tax under Income Tax Act. If you say the property disposed off was jointly held by multiple persons/family members, then the title deed and other revenue docs. must bear their name and other details. The parsons holding interest in the property has to share the sale proceeds in the proportion of their interest in the property and there should be documentary evidence to this effect. You can approach any experienced Income Tax lawyer or C.A. who will examine the docs and other evidences and suggest you on the tax liablity and procedure of compliance including scope of tax planning if any. It is better to approach the expert well ahead of the sale transaction.

Further, as you say, you have already met the tax liability arising out of the transaction,you can place the facts before the Expert for proper advice as regards sharing of the liability.