Section 12(6) in Karnataka Ayurvedic and Unani Practitioners' Registration and Medical Practitioners' Miscellaneous Provisions Rules, 1964
(6)An elector who has inadvertently dealt with his ballot paper in such manner that it cannot be conveniently used as a ballot paper may, on returning it to the Returning Officer and on satisfying him of the inadvertence, be given another ballot paper and the ballot paper so returned shall be marked "Spoilt, cancelled" by the Returning Officer. If an elector after obtaining a ballot paper decides not to use it, he shall return it to the Returning Officer, and the ballot paper so returned shall be marked as "Returned" "cancelled" by the Returning Officer. All ballot papers cancelled under this clause shall be kept in a separate packet.
