The Indian Citizenship Act does not allow dual citizenship. OCI is not a dual citizenship. If you ever held an Indian passport and if you acquire a citizenship of another country (such as the U.S. citizenship), you need to surrender your Indian passport immediately after you acquire foreign nationality.

The Indian government has observed that, even after acquiring foreign nationality, some people continue to retain their Indian passports and some even use them to travel and some people even renew them or avail of miscellaneous services for their Indian passport. Once you acquire the citizenship of another country, it is illegal to travel on the Indian passport. As India does not allow dual citizenship, holding a non-cancelled Indian passport after acquiring a foreign citizenship is an offense with penalties. The violators may be punished by imprisonment up to 5 years and with a fine up to $1,250. Actual penalties vary based on the duration for which the non-cancelled passport was kept, the number of trips made using an Indian passport after acquiring a foreign citizenship etc.

1. You acquired foreign citizenship on or before May 31, 2010.
   1. If you had your Indian passports cancelled on acquisition of foreign citizenship on or before May 31, 2010, no further action is required. You do not need a surrender certificate.
      
      To avail any consular facility such as OCI, PIO or Visa, you must show the proof that your cancelled Indian passport says 'passport cancelled on acquisition of U.S. (foreign) nationality'. If you are not able to produce such proof, a surrender certificate is required.
      
      
   2. If you didn't get your Indian passport cancelled by May 31, 2010, you need to apply for a surrender certificate with a 'miscellaneous service fee' of $20.
      
      
   3. If you were naturalized before June 1, 2010, but foreign (such as U.S.) passport was issued on or after Jun 1, 2010, the fee is $20.
      
      
   4. If you are a person of Indian origin who acquired the foreign nationality before June 1, 2010, but have lost or misplaced your Indian passport, you can't apply for getting it cancelled or for obtaining a Surrender Certificate. If you intend to apply for an India Visa / PIO Card or OCI card, you will be required to submit adequate proof to establish your Indian origin such as Indian naturalization certificate, birth certificate, land holding documents, house tax receipts, etc. You must additionally provide a copy of your naturalization certificate and Affidavit of Loss.
      
      
2. You acquired foreign citizenship after May 31, 2010.
   
   You need to apply for a surrender certificate with a fee of $175. In the UK, the fee is £90. This fee is actually Rs. 7,000, as set by the law.
   
   

If you are required to get a surrender certificate, the following penalties apply on a graded scale:

• If you used the Indian passport for travel, the penalty is $250 (Rs. 10,000) for each travel, maximum $1,250 (Rs. 50,000) towards travel. (New York: $1,250 anyway).
  
  
• If your Indian passport was renewed/reissued after acquiring foreign citizenship, the penalty is $625 (Rs. 25,000) for each renewal/reissue.
  
  
• If you availed miscellaneous services on retained/unsurrendered passport, penalty is $250 (Rs. 10,000) for each time of service.
  
  
• Passport lost/damaged or surrendered to a foreign government, no penalty.
  
  

Any of the fees and penalties above, as applicable, are in addition to the OCI, PIO or Indian visa fees and mailing charges. If your OCI or PIO card application is pending and if you need a surrender certificate as per the rules above, you must get it immediately before the your OCI/PIO application will be processed.