The oath of allegiance under sub-rule (1) shall be subscribed within a period of three months from the date of grant of certificate of naturalisation to which it relates, or within such extended period as the authority granting the certificate may permit, and in case the oath is not taken within the said period, the certificate shall be of no effect:  Provided that no permission shall be given under this sub-rule unless a statement to that effect is endorsed on the certificate and signed by the officer authorised under rule 15 to sign the certificate of naturalisation.

Citizenship Rules, 2009