THIRUVANANTHAPURAM: The filing of nominations for the Lok Sabha polls will begin on March 28. Nominations can be submitted before the Returning Officer, from 1100 hrs to 1500 hrs. Only five persons can accompany the candidate to the RO's office, a statement said.The last date for filing of nomination is April 4. The scrutiny of papers will be held on April 5. Election will be held in 20 constituencies on April 23.