All counties are now guaranteed four home ties over the six-week length of the tournament, which climaxes with the final at The Oval on July 31.
John Carr, England and Wales Director of Cricket said: "Domestic cricket is enjoying a well-earned renaissance.
"Talented players, close matches and some of the largest crowds on record are supporting the Twenty20 Cup."
Carr added: "With an exciting international season already announced for 2005 we anticipate a huge rise in the interest around the game as a whole.”
The competition began with 45 matches in 2003, expanding to 52 in 2004.
