Around 124,000 warning notices were issued to non-compliant vehicles seen using the zone in the first four weeks after expansion, between 25 October and 22 November 2021. Warning notices were issued to ensure the correct action is taken in the future and to allow for any genuine mistakes that may have occurred during the initial period of the expanded zone. This approach was also taken for the introduction of the central London ULEZ. Penalty Charge Notices (PCNs) were issued for contraventions from 23 November 2021. Transport for London publish a detailed breakdown of compliance, payments received and fixed penalty notices issued each quarter in a series of Ultra Low Emission Zone factsheets, which can be found online here: https://tfl.gov.uk/corporate/publications-and-reports/ultra-low-emission-zone.