Can I pay a surcharge on an off-peak train ticket to travel during peak hours?

Yes, it's called 'excessing' the ticket. Go to the ticket office first, and tell them you'd like to excess your off-peak into an anytime ticket, they'll charge you the difference and give you another ticket detailing the extra you've paid - sometimes they will staple it to your original ticket for you.

You can also do it on the train, but if you've boarded at a staffed station you *technically* have to do it at the station first - the guard does have discretion to excess your ticket on the train, but is also perfectly within his or her rights to make you buy a new ticket at full rate, because if you get on a peak train with an off-peak ticket, you're technically travelling without a (valid) ticket.

You can also 'excess' a ticket to carry on to a destination further than you originally intended, or to upgrade it from a super off-peak to an off-peak, or standard class to first class - you get the picture.

yes you can, what you are doing is called "excessing your ticket", if your excessing both ways, the difference is the price of an peak hours ticket, minus what you have paid, if only one way, the price will be halved, and that taken away from the single fare of a peak ticket for your journey.

You can upgrade at the travel centre before you board the train this is advisable, but if you don't have time and there are no barriers, seek the train guard and explain that you wish to travel on an a peak service, they cannot charge you a full single fare if you have a ticket and are willing to pay the upgrade

Upgrade Train Ticket

well it will be the same as not having a ticket. you will be travelling without a valid ticket. you do not have enough money to travel at peak times. get a life off peak tickets are for off peak times .

Badwolf if you were indeed an ex RPA you would know it doesn't matter if the passenger doesn't have time to get the fare excessed. The guard would be fully in his rights to refuse travel or make them pay full fare under the NCC.