The offer, for tickets bought from the website southeasternrailway.co.uk/sale, starts today (Wednesday 1 June) and runs until Wednesday 24 August.
The discount is an extension on last year’s offer, which ran from the middle of July to the same date in August – allowing passengers more time to get out and about during the warmer weather.
This is aimed at giving passengers more opportunity to visit, at a reduced price, the huge array of great destinations and hidden gems on the Southeastern network.
Discounts will include many standard Southeastern Off-Peak single and return tickets online, with no booking fees charged.
And tickets can even be bought on the day of travel, as long as people leave two hours between purchasing online and collecting it from a station ticket machine.
Southeastern Passenger Services Director Barbara Thomas said: “We really want to open up the great hidden gems that there are in Kent, East Sussex and London to our passengers at a reduced price.
“There are so many wonderful places on our doorsteps and we encourage all our passengers to take advantage of this offer during the summer months.”