The Nigerian forward was a key player in the Watford squad this season scoring 10 Premier League goals.
Dennis’ contract clause states that he would need to take a pay cut to stay with the Hornets in the coming season.
The Watford striker was signed last summer for just £3m. With four years left on his contract, his severance payment could provide a useful financial return despite Watford’s poor season.
According to the Mirror, West Ham manager, David Moyes is hoping spend money in the summer to sign at least one striker and two central midfielders.