The move follows the successful introduction of the Delay Repay system in late 2018 and will mean customers will be compensated if they reach their final destination 15 minutes later than expected, regardless of the reason.
Customers are now able to claim 25% of the cost of the single fare or 25% of the cost of the relevant leg of a return ticket for delays of between 15 and 29 minutes.
Delay Repay offers a wider choice of repayment options, including bank transfer, Paypal and charity donation to the Railway Children, a charity fighting for street children.
Head of Customer Experience for Transport for Wales, Barry Lloyd, described the change as "a huge benefit" for customers.
He said: "We're committed to delivering a punctual service that our customers can be proud of.
"A 15 minute delay is a big deal to our customers so this will be a huge benefit to them and shows our recognition of that. We've already moved to the Delay Repay system which makes claiming easier for customers and extending that to 15 minutes puts customers rightly at the forefront of our thinking.
"By offering customers compensation for delays of 15 minutes, we are setting ourselves a challenging goal in terms of our performance as we aim to be the best train operator in Britain."
Delay Repay gives customers a quicker response to their claim, as claims will now start to be processed within 48 hours of receipt. A system providing online access to customers’ individual claim history will allow customers to know exactly what’s happening with their claim and when it is complete. Customers must retain their tickets in order to claim.
Customers can claim by completing one of our claim forms or online https://tfwrail.wales/delay-repay-compensation