Tax liability in the case of Joint Ownership of Property

I'll break down the answers to each of your questions:

1. Joint Ownership and Sharing Ratio - As per the purchase agreement, Mr. X and Mr. B are joint owners of the flat. -

Since the sharing ratio is not explicitly mentioned in the agreement, it can be inferred that the ownership is held in equal proportion, i.e., 50% each. -

 However, it's essential to note that the sharing ratio can be disputed or clarified through a separate agreement or court intervention, if required.

2. Taxability of Mr. B's Share as Gift - As Mr. B is not a relative of Mr. X, the share of the property received by Mr. B can be considered a taxable gift under Section 56(2)(vii) of the Income-tax Act, 1961. - The fair market value of the share received by Mr. B would be considered as income and taxed accordingly.

 3. Ownership and Taxation after Mr. X's Death - After Mr. X's death, Mr. B would become the sole owner of the property, as per the joint ownership agreement. -

The transfer of property from Mr. X to Mr. B would not attract any income tax liability, as it would be considered a transfer due to death. -

However, Mr. B would need to obtain a succession certificate or a probate of the will (if any) to establish his ownership rights.

4. Compulsory Filing of Income Tax Return by Mr