Drivers of the most polluting vehicles will now have to pay a further £10 to enter the centre of London. Here's all you need to know about the toxicity T-charge.
:: Who will be affected?
Diesel and petrol vehicles, including HGVs, busses and coaches, registered before 2006 which do not meet the Euro 4/IV European directive to regulate vehicle emissions.
For motorised tricycles or quadricycles, they must meet the Euro 3 standard.
For newer vehicles, the Euro emission standard may be listed on your vehicles V5C document in section D.2.
Motorcycles, along with taxis and private hire vehicles licensed with Transport for London (TfL), are not subject to the T-charge.
A small number of "early adopter" vehicles manufactured before the Euro 4/IV standard became mandatory will have a NOx and PM emissions that meet the Euro 4/IV or better. These vehicles will not be subject to the charge either.
You can check if your vehicle is subject to the charge using TfL's T-charge checker.
:: What area does the T-charge cover?
It covers the same area in central London and operating times as the congestion charge zone, which is in operation between Monday and Friday, 7am to 6pm.
:: How do I pay the T-charge?
You can pay the £10 in addition to the £11.50 congestion charge online at tfl.gov.uk
TfL also has an auto-pay service, which you can set up through its website.
:: What if I don't pay?
You will receive a penalty charge notice of £130, which is reduced to £65 if it is paid within 14 days.
If it is not paid within 28 days, the fine rises to £195.
:: Can I get a discount?
If you are already registered for a congestion charge discount – other than the 9+ seater discount – it will also apply to the T-charge.
:: Why is this happening?
The move comes as part of TfL's attempts to improve air quality in London. Mayor of London Sadiq Khan insists "tackling poor air quality is a public health emergency that requires bold action".