Tens of thousands of passengers who were prosecuted and fined for fare evasion are set to be refunded after a judge ruled that their convictions were void.

Seven train companies including Northern Rail and Greater Anglia could face paying out millions of pounds to people who they privately prosecuted for travelling without a ticket under the controversial single justice procedure (SJP), despite not being permitted to do so.

In a ruling on Thursday at Westminster Magistrates Court, Chief Magistrate Paul Goldspring said six “test cases” should be declared “void”, adding that the cases of thousands of other cases would be dealt with in the same way over the coming months.

The judge said the Courts Service, the Department for Transport and the train operating companies – two of which have not yet been identified – would work to identify those affected, and that “a team will be put in place to begin the work of recovering the money paid and refund the money to individuals” by November.

“There are discussions ongoing with all the parties about how that may be paid,” he added.

Neither the amount of money to be refunded nor the number of people affected has been confirmed, but Judge Goldspring said “over 74,000” people is a “best guess at the moment”.

The SJP was set up in 2015 to allow magistrates to decide on minor offences, such as using a television without a licence or driving without car insurance, without defendants going to court.

Rail companies were permitted to use the SJP in 2016 to privately prosecute fare evaders, but many have been brought under the Regulation of Railways Act 1889, which is not allowed under the procedure.

In June, Judge Goldspring said those convictions were “probably unlawful”, with lawyers for rail companies telling a further hearing last month they were “in agreement” the prosecutions should be thrown out.

In his ruling, the judge declared the test cases a “nullity”, so it was “as if as though the proceedings never existed”.

He said: “Parliament did not envisage these offences being prosecuted through the SJP.

“They should never have been brought through that process.”

He continued: “I’m satisfied that the correct approach is to declare each of the prosecutions void and a nullity.”

He added that it was hoped that a list of those affected could be compiled by the end of September, with the cases listed as a “bulk” hearing “by the end of October” and declared void by a “similar direction” so that “everybody is in the same position”.

Following the ruling, the Ministry of Justice, the Courts and Tribunals Service and the Department for Transport said that the seven companies who had privately prosecuted fare evaders under the SJP were Northern, TransPennine, Avanti West Coast, Greater Anglia, Great Western Railway, Arriva Rail North and Merseyrail, with the list to be updated on Monday.

The departments said that those affected by the ruling were prosecuted by one of the seven companies between 2018 and 2023, with the “vast majority” of cases prosecuted from 2020, under either section 5(1) or section 5(3) of the Regulation of Railways Act 1889.

They added that those affected should wait to be contacted directly about their case.

They said: “The decision to use SJP is a matter for prosecutors. When cases come to court, magistrates decide on conviction and sentence, advised by legal advisers.”

Sarah Cook, whose prosecution was one of the test cases, said that the train companies admitting that her prosecution was wrong after fining her was “a kick in the teeth” and that the matter “puts a massive no-go” on travelling on trains.

Ms Cook, a 42-year-old pet shop owner from Barnsley, South Yorkshire, was fined £475 under an SJP prosecution after she did not pay a £20 fine for travelling without a ticket between Wombwell and Barnsley in November 2022.

But she said that she had been waiting to hear back for a year on an appeal against the original fine, before being told she had been prosecuted.

Following the court’s ruling, she said: “It’s a kick in the teeth. I know some people would say take the win, sit back, appreciate that. For me, although money at the time was an issue, for me more than the money was the stress.

“I have not got a criminal record, I’m not somebody out there committing crimes, and for somebody to say you could have a criminal record, you could potentially face jail time if you have been a repeat offender, to me that was terrifying.”

She continued: “For them, their punishment is ‘we’re sorry’, and there is a bit of me that thinks I don’t know if that is good enough.

“When you have put 75,000 people under the pressure of going to court, having to fill out multiple documents, potentially being threatened with larger fines and criminal records, I don’t know if ‘I’m sorry, here’s your money back’ is good enough.”

Tom Franklin, the chief executive of the Magistrates’ Association, called for reform of the SJP and said “serious questions” had been raised by the case.

He said: “This ruling has big implications for tens of thousands of people, and there are serious questions that the prosecuting authorities – in this case, the train companies – need to answer as to how this was allowed to happen.”

After Thursday’s hearing, a spokesperson for Northern Rail said: “We welcome the judgment of the Chief Magistrate in court today. We would like to apologise again for the errors that have occurred.

“We will now work with the court to implement today’s findings. We are unable to respond to individual inquiries in the meantime.

“Northern remains committed to ensuring that all our customers are treated fairly, which means ensuring all passengers who board our trains have a valid ticket.”

A Government spokesperson said: “We acknowledge the Chief Magistrate’s judgment and welcome the apology from train operators. While fare evasion should be tackled, the right process should be followed at all times.

“The people affected will be directly contacted in due course to resolve the cases in accordance with the judgment.”

A spokesperson for Greater Anglia said: “Following the hearing at Westminster Magistrates Court today we are now working to ensure all those who are entitled to compensation as a result of this procedural error are quickly and fully reimbursed.

“Like many in the industry, we acted in good faith following the introduction of the Single Justice Procedure in 2016, but we apologise for using this process incorrectly.”