Rental income from real estate investments in India is taxable under the Income Tax Act, 1961. The tax implications for NRIs and OCIs depend on whether they are considered a resident or non-resident for tax purposes.

For NRIs:

1. If an NRI is receiving rental income from a property in India, it is subject to a flat rate of 30% tax deduction at source (TDS), and the tenant is responsible for deducting the tax and paying it to the Indian government.
2. NRIs can claim certain deductions against rental income, such as standard deduction of 30% of the net rental income, interest on home loans, and property taxes paid.
3. NRIs can claim the benefit of the Double Taxation Avoidance Agreement (DTAA) between India and their country of residence, if any, to avoid double taxation on rental income.

For OCIs:

1. OCIs who are considered residents in India for tax purposes are subject to the same tax laws as resident Indians.
2. If an OCI is considered a non-resident for tax purposes, they are subject to the same tax laws as NRIs.
3. OCIs can also claim certain deductions against rental income, such as standard deduction of 30% of the net rental income, interest on home loans, and property taxes paid.
4. Like NRIs, OCIs can also claim the benefit of the DTAA between India and their country of citizenship to avoid double taxation on rental income.

In addition to the above, NRIs and OCIs need to be aware of the capital gains tax implications when they sell their real estate investments. They should also comply with the Foreign Exchange Management Act (FEMA) regulations when repatriating rental income or 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.