Inherited property

When any house property is received from INHERITENCE or by WILL, by a person ( here , your mother ) then there is no tax implication attracted on such property received by that person. Your mother is free from any kind of tax on such property from such transfer.

Moreover, the implication of Capital Gain tax arise on your Grandfather as he has ultimate ownership of house at time of transfer. So your.mother is free from hetting any kind of tax.implication. However your grandfather may get such implication.

My grandfather is 80 plus and does not have pan card i.e.not filed any return yet in his lifetime... What process u suggest to do...? If he does not file any return and did not intimate to IT department regarding such sale....will any tax liability occur towards my mother in future years..?say after 4-5 years later....

Yes, grandfather will have to get a PAN and file ITR and show this transaction. One can save capital gain by investing in bonds or another property. If he receives a notice of demand for the capital gain, then he will be liable to pay the tax. If he is no more, then his legal representative shall be liable to pay tax.