The agreement comes after the club posted losses of £4million for the last 12 months, an increase of £3.4million from the previous year.
In a statement on the Lions' website, chairman John G Berylson, who also runs CHV, said: "This shows our continued commitment to Millwall FC.
"We have stated in the past that we see this as a long term plan and I am delighted the club continues to make progress both on and off the field.
"Too many clubs in the past have gone through boom and bust in their attempts to get to the Premier League. Millwall is committed to getting there in a sensible way that doesn't threaten the club's long-term viability.
"Developing The Den and our surrounding area will help to future proof our prospects and success."