By Ross Lydall

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About £800m is owed to Transport for London by motorists who have refused to pay Sir Sadiq Khan’s Ulez ultra-low emission zone charge.

The mayor extended the £12.50-a-day levy across all 33 boroughs in Greater London in August 2023, despite opposition from many motorists and a number of Tory boroughs.

The vast majority of vehicles driven in London – more than 97 per cent – are compliant with the Ulez’s exhaust emission rules and their drivers do not have to pay the daily charge.

But drivers of older vehicles that do not meet the emission standard do have to pay – and face fines of £180 a day if they fail to do so.

The extent of TfL’s unrecovered Ulez debt emerged on Friday as TfL outlined its latest efforts to crack down on persistent offenders.

TfL has seized more than 530 vehicles in the first half of 2025, and generated £285,000 by selling 350 of them them at auction. Other vehicles are crushed.

In total, TfL recovered £16.5m of Ulez debts over the six-month period, with the money being reinvested in the capital’s public transport network.

However, by April, it was owed £789.1m in unpaid Ulez fines, also known as penalty charge notices (PCNs) – though it did expect a number to be paid.

TfL said that 94 per cent of its Ulez debt was owed by “persistent evaders” – drivers with at least four unpaid PCNs.

About 28,500 drivers a day pay the Ulez – but 5,000 fail to do so and are sent a PCN.

TfL continues to have problems with vandals wrecking Ulez enforcement cameras.

Enforcement action is triggered when drivers fail to pay over an “extended period”. This involves issuing warrants. Enforcement agents will visit the driver’s home address.

In one case, a driver who was traced to a new address eventually agreed to pay £6,800 after receiving 18 warrants.

Another driver paid almost £17,000 to clear 46 warrants.

A car that was linked to 88 warrants was sold for £7,000 at auction. More than 130 letters had been issued to the driver and they were visited 14 times.

One driver refused to pay, leading to his vehicle being located and seized. It raised more than £2,100 at auction.

TfL is making greater use of civil action as part of a tougher approach to enforcing the Ulez.

In the most extreme cases, this could lead to bankruptcy proceedings for an individual or business if they refuse to settle.

Alternatively, TfL could seek to recover earnings from an individual’s employer.

Alex Williams, TfL’s chief customer and strategy officer, said: “Most drivers who have vehicles that are liable for the charge are responsible and pay it. It is only a small group of persistent evaders who fail to do so.

“We want to make it clear that if you receive a penalty charge for driving in the zone, you should not ignore it.

“There is a risk that your vehicle and other items of property will be removed. If you’re ignoring it because you are facing financial difficulties, please instead engage with our staff.”