Sadiq Khan’s Ulez has been grappling with an enforcement crisis after reports found that drivers have been failing to pay the fines resulting in millions of uncollected penalties.
The figures, disclosed in a Freedom of Information request, revealed that 2.9 million outstanding penalty charge notices remain unpaid despite extensive enforcement efforts.
The transport authority has passed more than 4.1 million warrants to enforcement agents, yet the vast majority of fines remain uncollected.
This mounting debt has now raised serious questions about whether TfL's penalty system can effectively enforce compliance with London's air quality schemes.
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The scale of non-payment suggests fundamental weaknesses in the collection process, particularly as the authority pursues stronger civil enforcement measures.
The FOI response, published by TfL, breaks down the staggering scale of unpaid charges across both emission zones.
For Ulez alone, 2,934,089 penalty charge notices remain outstanding from warrants issued to enforcement agents while the Low Emission Zone adds another 19,564 outstanding penalties to this total.
These figures emerge from 7,519,237 Ulez penalties issued since 2020, with 4,714,058 progressing to Charge Certificates when initial payment deadlines were missed.
London Mayor Sir Sadiq Khan has praised the Ulez scheme despite millions of unpaid penalties
| PASubsequently, 4,367,728 advanced to Orders for Recovery, and 4,110,555 reached the warrant stage requiring enforcement agent intervention. The LEZ showed a similar pattern, with 71,004 penalties issued resulting in 32,871 warrants to enforcement agents.
Despite this extensive legal escalation process through the Traffic Enforcement Centre at Northampton County Court, collection rates remain remarkably low, according to reports.
Meanwhile, TfL's enforcement efforts between January and June 2025 yielded £16.5million in recovered debt across all road user charging schemes, the transport authority stated. Enforcement agents seized more than 530 vehicles during this period, with over 350 sold at auction, generating approximately £285,000.
Notable cases include one driver paying £6,800 to clear 18 warrants after agents traced them to a new address, whilst another settled £17,000 for 46 warrants following repeated contact.
The Ulez penalty notices first started being sent out in 2021 | PALATEST DEVELOPMENTS:
In one extreme instance, a vehicle linked to 88 warrants was seized after the owner ignored more than 130 letters and 14 visits, eventually raising £7,000 at auction. In another case, a persistent evader’s vehicle fetched £2,100 at auction after they refused payment demands.
TfL has now begun trialling alternative civil enforcement methods to strengthen debt recovery, though the FOI response confirmed that no penalties have yet been collected through these new approaches.
The transport authority stated it is "making greater use of powers and working with the Government to strengthen measures that will bring those who persistently fail to pay the charge to account."
Potential measures under consideration include bankruptcy proceedings for individuals or businesses refusing to settle debts, and actions ensuring repayment before property sales. Other options being explored encompass recovering earnings directly from employers and pursuing debt recovery through County Court proceedings.
The Ulez was expanded across Greater London in 2023 | PAThe FOI response explicitly stated that TfL has not applied for Third Party Debt Orders or similar court interventions to recover unpaid penalties. The concentration of debt among repeat offenders presents a stark picture of TfL's enforcement challenges.
According to the transport authority, 94 per cent of all outstanding Ulez penalty debt comes from persistent evaders who have accumulated at least four unpaid charges.
This occurs despite more than 97 per cent of vehicles observed in London meeting Ulez emission standards, indicating the problem stems from a small minority of drivers.
TfL's policy allows penalty balances to be written off after lying dormant for two years following warrant expiry, subject to a strict validation process.