Book early and save: Yes
Online bookings open: 6 months ahead of the travel date
The discounted tickets are the 'Sparscheine' tickets and they can be booked online up until the day of departure, but they can't be booked at stations, so booking last minute at the station is always more expensive.
Though you'll usually need to book the 'Sparscheine' tickets at least a couple of days ahead to obtain them at the cheapest possible price.
Trains departing at different times can also be cheaper than others leaving on the same day, so you may need to look through the day's departures to find the cheapest fares.
It can pay off to take a look at the guide to Austrian train tickets - it should help you save time and money and confusion.
Exchanges and Refunds
Book a Non-Flex ticket or a Semi Flex Ticket and it will be specific to the departure you selected when making a booking
Meaning that if you arrive at a station too late to board a train because your taxi got stuck in traffic, or there was a fault on the tram etc, you will have to pay the full price at the station for a replacement ticket.
The only scenario in which these ticket types can be used for an alternative, later departure is IF your journey involves more than one train AND a delay to an OBB train causes you to miss the departure you were booked on to.
Non-Flex and  Semi Flex Ticket tickets also can't be exchanged to an alternative departure pre-travel.
However, if post-booking you subsequently change your travel plans, you can cancel a Semi Flex ticket and receive 50% of your payment, but Non-Flex tickets can't be refunded at all - And that is the key distinction between the two types of ticket!
These terms also apply if you want to use Semi Flex and Non Flex tickets to travel in First Class!
If you will want to have the freedom to both refund your ticket and take any train on your travel day, you will need to pay extra for a Flex ticket.
Seat reservations
Reservations are available, but optional for journeys for journeys within Austria by Railjet trains.
Therefore, seats on the train you will be travelling are NOT absolutely guaranteed if you haven't reserved.
Though the OBB online booking service now indicates whether a specific departure is proving to be exceptionally busy.
Reservations in both 1st class and 2nd class cost €3 per person when booking Non-Flex and  Flex tickets, but are included as a complimentary benefit when booking Semi-Flex tickets
Reservations for travel in Business Class cost €15 regardless of the type of ticket booked.
Note that reservations will also be required any children aged 5 to 15 - children aged 4 and under don't require tickets, but the expectation is that they will be travelling in the adult's lap.
Child tickets
When booking 'Sparschiene' tickets each adult (aged 15 and over) can take up to four children aged 14 and under for free!
These children will still require tickets, but there will be no charge for them.
When not booking 'Sparschiene' tickets;
- Children aged 5 and under travel for free
 
- Children aged 6 – 14 travel at half-fare
 
Bike tickets
You will need purchase both a bike ticket AND a reservation for your bike prior to boarding; more info on how to do this is available on the [bikes on trains guide](/travel-info-and-tips/taking-a-bike-on-a-european-train/).
Dog tickets
If your dog is too large to be taken in a pet carrier you will need to add a dog ticket when making your booking;
Using rail passes
If you have a valid Eurail or Interrail pass you can opt to make reservations for this journey, but you can simply board with a pass and hope that seats will be available.