Tickets bought directly on the GoEuro website may be cancelled if allowed by their terms and conditions.
Have you purchased your journey on a partners website, you'll need to check cancellation options with the transport provider.
To be sure of your cancellation options before you book, once you're on the page listing all of the potential transport options, click on the small (i) icon next to the price. This should then show you all the cancellation information regarding your chosen route. Additional information will also be provided during the booking process. Discounted or reduced tickets cannot be changed or cancelled.