A compensation scheme brought in following the introduction of new rail timetables will be extended to part-time workers.
Govia Thameslink Railway (GTR) announced that some customers who made return trips on at least three days in any week between May 20 and July 28 will be eligible for a pay out.
The enhanced compensation was previously only available to people who held weekly, monthly or annual season tickets.
Only passengers who travelled on Great Northern or Thameslink services from the most affected stations will be able to claim.
The value of the pay outs will vary depending on the number, cost and type of tickets bought.
Passengers are advised to retain any tickets, receipts or other proof of travel to support their applications.
The damaging impact of the new timetables is demonstrated in punctuality figures published by Network Rail.
More than a third (36%) of Thameslink trains were delayed by at least five minutes between May 27 and June 23, compared with 18% in the same period last year.
The proportion of Great Northern trains failing to hit the same punctuality target rose from 16% to 30%.
GTR chief executive Patrick Verwer said: “We have listened to feedback.
“We believe it is right to extend the compensation scheme beyond season ticket holders to other regular travellers.
“We are sorry for the disruption in the weeks that followed the May timetable change.
“Overall, the train services on Thameslink and Great Northern have been stable, more reliable and more frequent since the introduction of the interim timetable on 15 July.
Anthony Smith, chief executive of independent watchdog Transport Focus, said: “Regular passengers, such as part-time workers, affected by timetable disruption deserve compensation.
“Widening compensation to non-season ticket holders who travel regularly is a welcome step in rebuilding passengers’ trust.
“It’s now important that train companies actively encourage passengers to claim and make it both quick and easy to do so.”
GTR said it would begin contracting qualifying season ticket holders this week.
The enhanced compensation is being offered in addition to the standard Delay Repay, which makes pay outs for individual journeys delayed by at least 15 minutes.