Tickets for Bernina

Hi
Could you possible answer a question for me I have been looking on the internet for a correct response but to no avail. We are travelling on the Bernina Express from Chur to Tirano on 28th July. We have made an online seat reservation and have received the relevant email confirmation.
Is is necessary to buy a ticket in advance or does the reservation hold the seats until the day, when we pay on the train/at the station
Thanks in advance
Michelle

Hello Michelle, and welcome to the forum! If you already have your seat reservation, you don't have to buy the ticket itself well in advance. You can even do so right before boarding at the railway station of Chur.

By the way, will you be using any of the Swiss rail passes? If so, you may not have to buy a ticket at all but just show your pass.