Rail passengers could be entitled to compensation after Northern was accused of breaking its fare evasion rules to prosecute commuters.
The train operator said on Monday all prosecutions of people accused of using a 16-25 railcard to obtain a discount at the wrong time of day were being withdrawn and thousands of previous cases reviewed.
The company was criticised for prosecuting young people after they used their railcards in a way that would have saved a few pounds on morning journeys.
Under Northern rules, passengers with a railcard travelling on the wrong train must be offered the chance to pay back the deficit on the spot, the Telegraph reported.
A Northern spokesperson said: “We understand that fares and ticketing across the railway can, at times, be difficult to understand, and we are reviewing our processes for ensuring compliance with ticket and railcard terms and conditions.
“With regard to recent reported cases involving use of the 16-25 railcard with fares under £12 before 10am, we are withdrawing any live cases and will also look to review anyone who has been prosecuted previously on this specific issue.
“We are actively engaged with government and industry to simplify fares to help customers.”
Restrictions on a 16-25 railcard, which can also be bought by full-time students, mean discounts can only be applied to an “anytime” ticket before 10am if the fare is £12 or more, requiring cardholders to pay full fare for cheaper tickets.
However, there are exceptions to this rule: railcards can be used on early morning trains at a weekend, or during the months of July and August.
Some rail users said the rules were confusing and they had fallen foul of the regulations after buying discounted tickets, unaware that their railcards were not valid.
Sam Williamson, 22, received a letter from Northern threatening him with prosecution over a £1.90 fare discrepancy after he mistakenly used his railcard on a morning train from Manchester to London on 5 September.
Last week, in a social media post seen by millions, Williamson said he had received a letter from the government-owned operator threatening him with legal action.
The engineering graduate from Glossop, Derbyshire, said he was subsequently contacted by the train operator notifying him that it would “be taking no further steps” against him.
A Department for Transport spokesperson said: “We expect Northern and all operators to ensure their policy on ticketing is clear and fair for passengers at all times. Northern are reviewing the details of these cases and will report back to the department.
“It is clear that ticketing is far too complicated with a labyrinth of different fares and prices, which can be confusing for passengers. That’s why we have committed to the biggest overhaul of our railways in a generation, including simplifying fares to make travelling by train easier.”