1. All matches are 20 overs per side, with the teams divided into three groups - North, Mid/West/Wales and South.
TWENTY20 CUP GROUPS
Derbyshire, Durham, Lancashire, Leicestershire, Nottinghamshire, Yorkshire
Glamorgan, Gloucestershire, Northamptonshire, Somerset, Warwickshire, Worcestershire
Essex, Hampshire, Kent, Middlesex, Surrey, Sussex
2. Most matches start at 5.30pm, with a 15-minute interval before the start of the second innings, but some may begin at 7.30pm to allow play under lights.
3. Each innings should last no longer than 75 minutes, equating to an average of three minutes 45 seconds per over.
4. Teams will incur a six-run penalty if they fail to bowl the full 20 overs within the 75 minutes.
5. Batsmen must be ready to take guard or in position at the bowler's end within 90 seconds of a wicket falling.
6. Only two fielders are allowed outside an inner circle for the first six overs of a team's innings.
7. Individual bowlers are permitted a maximum of a fifth of the total overs in a completed innings ie four overs if there is no delay or interruption caused by rain.
8. Umpires can impose a five-run penalty for time-wasting by batsmen. They are expected to be ready as soon as the bowler is ready.
9. No-balls will be penalised by a free-hit next ball - a batsman cannot be out from a free-hit delivery unless they are run out.
10. Each side must face a minimum of five overs to constitute a match. The Duckworth-Lewis method will be used to calculate run targets in rain-affected games.
11. The three group winners, three second-placed teams and best two third placed teams will go through to the quarter-finals on 24 July. The winners of those games progress to semi-finals/final day at Trent Bridge on 12 August.