Complex sentence: By September 2015, the first phase was completed; over 66.90 lakh (6,690,000) households submitted forms linking themselves to either the NRC of 1951 or any of the electoral rolls prior to 24 March 1971.
Split into simpler sentences: By September 2015, the first phase was completed. Over 66.90 lakh households submitted forms linking themselves to either the NRC of 1951 or any of the electoral rolls prior to 24 March 1971.