In case an OCI card holder below the age of 20 years has not got OCI card re-issued on change of passport, he/she may travel on the strength of his/her existing OCI card bearing old passport number subject to the condition that along with the new passport, the OCI cardholder carries old passport mentioned in the OCI card.

In case an OCI card holder who has attained the age of 50 years and got his/her passport renewed subsequently but has not got his/her OCI card re-issued on renewal of passport, he/she may travel till June 30, 2020 on the strength of existing OCI card along-with the new and old passports.
It is, however, advised that OCI cardholders may take steps to comply with the existing OCI guidelines in Para 1 above and renew their OCI cards as required by the rules.

https://www.mea.gov.in/press-releases.htm?dtl/32222/Press+release+on+Relaxation+in+OCI+Guidelines+till+30th+June+2020

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