This has been a long-standing issue for part-time workers, especially those commuting long distances.
In England, you may be able to save by getting a flexible season ticket – they allow you to travel as a day return on any eight days in a 28-day period using a paperless ticket via a smartcard or phone, and you don't need to select when you want to travel in advance. They can be used on both peak and off-peak travel, and at weekends.
In 2021, we did some research that showed while some can save £100s a year, others will save little or would even be worse off. See our full flexible season ticket analysis.