There is no Indian exit tax
The first thing people fear is a US-style exit tax, a deemed sale of everything you own the day you expatriate. India has nothing like it. There is no exit tax, no expatriation tax and no deemed disposal of your assets when you give up Indian citizenship or surrender OCI. It helps to be precise about why: it is not that a section of the law exempts you, it is that no such charging provision exists at all. India taxes actual gains on actual sales, and it taxes on the basis of residence, not citizenship. So the act of renouncing, by itself, triggers no Indian tax.
One honest caveat so this is not misread. India will still tax you in the normal way when you later sell an Indian asset, a property, shares, a mutual fund, at the capital gains rate that applies to a non-resident. That is an ordinary sale being taxed, not a charge for leaving. What you avoid is any tax purely for changing citizenship. On the mechanics, under Section 9 of the Citizenship Act, 1955 your Indian citizenship ends automatically the moment you voluntarily acquire another country's citizenship, India does not allow dual citizenship. You then surrender your Indian passport and obtain a renunciation or surrender certificate, and can separately apply for OCI, which is a lifelong visa, not citizenship. Surrendering OCI is again a separate process with no tax consequence.
What actually changes is your FEMA status
The real consequences of becoming, or already being, a person resident outside India are under FEMA, not income tax. Your resident savings and current accounts must be redesignated as NRO accounts, or moved to NRE or FCNR, this is a compliance obligation, not a tax event. Note too that your tax residency is a separate question decided only by your days in India under Section 6 of the Income-tax Act, so losing your citizenship does not, by itself, make you a non-resident for tax or change how your income is taxed.
A few investments have special rules, and this is where old advice online is wrong. A PPF account opened while you were resident can be kept and contributed to until it matures, on a non-repatriable basis, but it cannot be extended beyond maturity, and you cannot open a new PPF as an NRI. NSCs held from before can run to maturity but cannot be renewed or freshly bought. Ignore the older articles that say these accounts close the day you become an NRI, that came from a 2017 notification that was withdrawn. On property, you can hold and inherit agricultural land, a farmhouse or a plantation, but you cannot buy them, and inherited agricultural land can usually only be sold to a resident Indian. None of these is a tax on renunciation, they are just the rules that apply once you are a non-resident. A practising CA helps you redesignate accounts, handle the PPF and NSC correctly, and plan any later asset sale.