It was announced today that the average season ticket price could increase by 3.5% in January.
That's based on today's inflation figure of 2.5% - and another 1% added on top for investment.
But with train companies allowed to put tickets up by another 2% - it means commuters could face a hike of over 5%.
Which could mean commuters forking out an extra £400 a year.
Responding to the publication of July’s Retail Price Index (RPI) inflation figure of 2.5%, which helps determine season tickets and other regulated train fares for 2015, an Abellio Greater Anglia spokesperson said:
"Government decides the average change to regulated rail fares, including season tickets, each year. The details of changes to rail fares will be confirmed later in the year. We recognise and share the importance that rail passengers place on value for money and improving train services in our region, and we're working with our stakeholder partners on initiatives including the taskforce which has been established to make the case for greater investment in the Norwich to London mainline.
"We have also worked with the Department for Transport to secure a £20 million investment in a package of service enhancements to be delivered during the current franchise to October 2016, including a major refresh of the carriages on our Norwich to London intercity services, and more capacity.
"We will also continue to build a positive case for the next long franchise to help in bringing about the major enhancements to rolling stock and infrastructure for the East Anglia rail network that we all wish to see."
What could the impact of rail fare rises be on your wallet? Compare selected season tickets before and after the forecasted rise.Read the full story ›
Rail Minister Claire Perry said she sympathises with passengers who have had to contend with "inflation-busting fare rises almost every year over the last decade" but insisted the Government was committed to "fair fares".
What we have got to do is make sure rail passengers, who could be forgiven for thinking 'What on earth am I getting for these rises I've seen over the last decade?', start to realise that they are paying fair fares for comfortable commuting.
The RMT union, which campaigns for the railways to return to public ownership, has said that next year's fare rise is a "kick in the teeth" for rail passengers.
With the “flex” rule passengers are facing fare increases of up to 5.5% at a time when wages are stagnating. People will simply be priced off the railways while the greedy train operating companies are laughing all the way to the bank. This is a kick in the teeth for the millions of British people who use our trains ... With Northern Rail already axing off-peak tickets, with others set to follow, we are once again ratcheting up the highest rail fares in Europe to travel on some of the most clapped-out and overcrowded services ...
Rail fares could rise by as much as 5.5% next year under the current system, ITV News' Consumer Editor Chris Choi reports:
Train fares - under current formulae some could increase to 5.5%
Rail passengers will see the average price of their tickets increase by 3.5% from January, according to figures out today.
"We're a victim of our success" Michael Roberts, Director General of the Rail Delivery Group, representing train operators and Network Rail, said.
Mr Roberts told Good Morning Britain that the UK's trains are so busy because they are affordable, refuting claims that fare hikes are pricing people out of rail travel.
Rail travel is being pushed "out the reach of some ordinary people" by fare increases, the head of a public transport advocacy group said.
Stephen Joseph, executive director of the Campaign for Better Transport, told Good Morning Britain that Government-dictated ticket price hikes mean rail fares are rising four times faster than wages.
Commuters will find out how much rail fares are likely to rise by next year when the Retail Price Index (RPI) for last month is released today.
The annual increase is capped at July's RPI plus 1%, with an extra 2% added to some tickets.
The cost of some train tickets could be almost 6% higher next year.
Rail commuters will be paying close attention to the announcement of last month's Retail Prices Index (RPI) figure today, as it will be used to calculate increases to next year's regulated fares, including season tickets.
Ticket price rises are capped at 1% plus the July RPI figure, expected to be around 2.6%.
Train companies can add another 2% to some fares, as long as the overall average remains as per the formula.
Campaigners say ticket prices are rising four times faster than the average wage and that the measurement used to calculate fare increases has been discredited.