Open Returns are flexible tickets as you do not need to specify the exact time and date you want to return on.
If you've purchased an Off-Peak or Super Off-Peak ticket, you can change the time of your outbound date, but must travel on the date specified on the ticket. An Anytime ticket can be used on the outbound journey for the date specified on the ticket and any day up to 4 days later.
All you need to do is make your return journey by the date specified, typically 28 days after the outward journey. Tickets with the name 'Day' (such as Anytime Day Return) only allow you to return on the same day as your outward journey.
There are 3 types of Open Return tickets available each with varying flexibility and cost:
Anytime Return – no restriction on return travel.
Off-Peak Return – return travel permitted Off-Peak trains only.
Super Off Peak Return - return travel restricted to only Super Off-Peak trains.
If you want to know when you can travel please see: When can I use Off-Peak and Super Off-Peak tickets?