Advance tickets (which are valid on a specific train only) for travel up to 30 September 2022 can have their date and time changed for free up until 18:00 the day before. If the price of your new ticket is more expensive, you'll need to pay the difference.
If you don’t know when your new journey will be, you can ask for a travel voucher instead. This will be valid for 12 months.
Off-Peak and Anytime tickets can also be changed free from admin fees, up to the date of departure.