After you get British Citizenship for up to three months, you can travel on your Indian passport. The three-month period is calculated from the date of acquisition of foreign nationality on the certificate of naturalization.
The Indian passport is an offense under the Indigenous Passport Act 1967 after the three-month grace period of being abroad citizens.
Certain people still hold their Indian passports and even use them for travel even after they become foreign citizens (and renew them on expiry).
Once a foreign national is obtained, travelling on an Indian passport shall not take place after the expiry of the grace period.
If you do, you might be penalized. The sanctions are calculated at a graded level depending on the number of trips you made after obtaining foreign nationality on Indian Passports.
Consequences of not surrendering your Indian passport
As mentioned on VFS:
“The Indian passport misuse penalty would be imposed if the last Indian passport held expired on or after 1 January 2005 and remained after 3 years, e.g. not abandoned or traveled by the PIO for a period of three months, or renewed after the foreign citizenship acquired by the last Indian passport held”
You will send a report to the High Commission of India in the UK, explaining the reasons, if you fall into one of the situations above.
In the case of a fine, it may not be suspended or decreased in accordance with the rules on the VFS website. In the past customers have got fined £ 1200– so it doesn’t mean that you catch them now. In the future, you need a service, and then they check and fine you.