The process to file nominations for the presidential election began on Wednesday with the Election Commission issuing a notification calling upon the electors to fill the vacancy.
The election is scheduled to be held on July 18.
The nomination process began on a day when various opposition parties are meeting in Delhi to decide on a presidential candidate.
The nominations can be filed till June 29 and the scrutiny of the papers will take place on June 30. July 2 has been decided as the last date of withdrawing from the electoral battle.
The counting will be held here on July 21.
The term of incumbent President Ram Nath Kovind ends on July 24.
The president is elected by the members of the electoral college consisting of elected members of both houses of Parliament and elected members of the legislative assemblies of all states, including the National Capital Territory of Delhi and the Union Territory of Puducherry.
The nominated members of either Rajya Sabha and Lok Sabha or legislative assemblies of the states are not eligible to be included in the electoral college and, therefore, they are not entitled to participate in the election. Similarly, members of the legislative councils are also not electors for the presidential election.
While voting takes place in Parliament House and state legislative assemblies, the counting of votes is held in the national capital.
Leaders of some major political parties held hectic parleys on Tuesday ahead of a meeting called by West Bengal Chief Minister Mamata Banerjee here on Wednesday to forge a consensus for fielding a joint candidate against the NDA in the presidential election, a move that has exposed the fault lines within the opposition.