Rail passengers could save money just by asking a few simple questions, a national passenger group says.
Season tickets and saver fares rose by an average of 4% this month
The Rail Passengers Council (RPC) says hundreds of pounds in compensation and discounts may not be being claimed.
It has published an advice leaflet called "Get the Best Deal" which tells passengers how to get all they are due.
RPC explains that claiming poor performance discounts on monthly or annual season tickets could save hundreds on a renewed ticket.
For example, passengers travelling between Leicester and Birmingham who ensure that they are given their 10% discount for poor performance would save £219.
The RPC, which acts as a voice for rail passengers, said the most common situation where passengers might be missing out occurred with "void days".
These are days where train companies cannot run an effective train service so declare the day void and must pay compensation.
To do so, passengers had to ask or remind train company staff if they were entitled to void day compensation but on the Fleet, Hampshire to London service it gained them more than £50 in compensation.
The RPC also says that with passengers already facing above-inflation fare rises, they need to make the most of benefits provided by season tickets.
The RPC said the compensation should be given by rail companies automatically when season tickets were renewed.
"It is difficult to get the figures on exactly how much money is being missed out on", said RPC Communications Manager Caroline Jones.
"But we've had quite a few complaints from people told that they had to claim the money at the time of renewal and that it was too late."
She said they are trying to make people aware of this now, as January and February are when around 60% of commuters renewed their tickets.
"We want to empower passengers by making sure they ask the right questions," she said.
The Association of Train Operating Companies (ATOC) agreed that it would "probably be wise" for commuters to ask about any compensation due when they renewed season tickets.
Communications manager for ATOC John Dennis said discounts applied when train firms did not meet the Strategic Rail Authority's performance targets on punctuality and reliability.
"It should be automatically applied but there have been occasions when it has not, particularly when void days haven't been offered," he said.
He said information on how a rail firm had performed was displayed at most manned stations.
However, Mr Dennis said it was important to keep "things in perspective".
"In the main ticket office staff are very good at offering these discounts."
The RPC leaflet also reminds passengers of a range of railcards and offers available which could make journeys much cheaper.
For example, commuters travelling in London and the south east on an annual ticket can buy a Network Railcard for a friend or family member for £1 instead of £20.
The RPC will give the leaflet to commuters on its database. It will also be available at some stations, online and at events the passenger group will hold across the country.