Bonfield's move will help him be closer to his family, National Grid said, without identifying the U.S. company.

Andy Agg, currently group tax and treasury director, will hold the position on an interim basis while the board looks to identify a permanent successor, National Grid said.

Bonfield, who has been CFO since November 2010, will step down after National Grid's annual general meeting on July 30.

He will receive his normal salary and associated benefits until his leaving date, including his annual bonus for 2017/18, National Grid said, adding that all outstanding awards as at July 30 will be forfeited.

Bonfield was previously CFO of Cadbury Plc and Bristol-Myers Squibb, and finance director at BG Group plc. He was also named to Reckitt Benckiser board in March.

(Reporting by Arathy S Nair in Bengaluru; Editing by Kevin Liffey)