What types of ticket can be refunded? Follow

Flexible tickets (Off-Peak, Super Off-Peak and Anytime tickets)

These types of ticket can be refunded online for a fee. 

You have 28 days from expiry of the ticket to request a refund. If you have a mobile ticket and it has already been activated, you can no longer claim a refund on that journey.

Advance Single ticket

Advance Single tickets cannot be refunded but they can be changed.

Changes are only allowed for a different time/date of travel, so you need to stick to the same departure and arrival stations.  Visit this page for more information on changing.