Capital gains tax is applicable to real estate investments in India, and NRIs and OCIs are subject to different rules depending on whether they are considered a resident or non-resident for tax purposes.

For NRIs:

1. If an NRI sells a property in India after holding it for more than two years, they are liable to pay long-term capital gains tax (LTCG) of 20% on the gains. The gains are calculated as the difference between the sale price and the indexed cost of acquisition.
2. If an NRI sells a property in India within two years of acquiring it, they are liable to pay short-term capital gains tax (STCG) at the applicable slab rate on the gains. The gains are calculated as the difference between the sale price and the cost of acquisition.
3. NRIs can claim indexation benefit on the cost of acquisition, which takes into account the inflation during the holding period, while calculating LTCG.
4. NRIs can also claim exemption from LTCG tax by investing the gains in certain specified bonds or by reinvesting them in another property within a specified time.

For OCIs:

1. If an OCI is considered a resident in India for tax purposes, they are liable to pay tax on their global income, including capital gains from real estate investments.
2. If an OCI is considered a non-resident for tax purposes, the rules for NRIs mentioned above apply.

In addition to the above, NRIs and OCIs need to comply with the Foreign Exchange Management Act (FEMA) regulations when repatriating sale proceeds to their country of residence or citizenship.

It is recommended that NRIs and OCIs seek professional advice from experts in real estate, taxation, and legal matters before making any investment decisions.