Season ticket prices face a rise of 1.6% in Kent despite workers avoiding rail travel as lockdown eases.
Some routes may see a rise of over £100 when prices are set to increase some time next year.
Though rail fares usually go up in January, it is thought increases will be delayed further into 2021 due to low passenger numbers. This will likely be confirmed in November.
Season ticket prices are based on the July Retail Prices Index (RPI) inflation measure and are regulated by the government during their change every year.
High speed commuters to London could see fares exceeding £7,700 a year in areas such as Canterbury and Ashford - a rise of over £120 a year.
The announcement comes as workers are encouraged to return to their offices as lockdown eases, but high prices may push more to continue working from home.
Train use is still below a third of what it was before lockdown despite car use almost returning to pre-pandemic levels, according to the Department for Transport.
Anthony Smith, chief executive of watchdog Transport Focus, said: “Our research tells us almost two in three former rail commuters expect to work from home more so we will probably now travel less for work, both commuting and on business.
“The government must go above and beyond a fares freeze and get train companies to offer a combination of cut-price deals, carnet-style ‘bundles’, flexible season tickets for commuters and better-value-for-money fares across the board.”
At the start of this year, season tickets rose by 2.7%, which the The National Union of Rail, Maritime and Transport Workers (RMT) called "a kick in the teeth for the UK’s rail passengers."
This year, the union is calling for fares to be cut by 5% each year and have been campaigning for the rail networks to be nationalised so funds can be invested into services.
RMT senior assistant general secretary Mick Lynch said: “After well over a decade of eye-watering fare increases and with an industry in crisis, tinkering with fares is simply not good enough.
“Instead we argue that stopping the unjustified profiteering of the train companies would pay for an annual 5% cut in fares as part of a long-term national strategy for our railway.”