Most people have welcomed the charge, which is aimed at improving air quality, but some are unhappy. We spoke to both sides to get to the heart of the matter.
We spoke with a business leader, an environmental scientist and a motorist to find out the impact of the London T-Charge.
The T-Charge legislation enforces all vehicles driven in central London to meet a minimum Euro emission standard. If they don't, drivers must pay the daily charge of £10, on top of the £11.50 congestion charge.
However, as it is when assessing car insurance, the type of vehicle is taken into account when evaluating the minimum Euro emission standard:
There are vehicles that don't have to pay the charge, including taxis, motorcycles, scooters, emergency-service vehicles and breakdown vehicles.
Currently, the highest rating is Euro 6 for light-duty vehicles and Euro VI for heavy-duty vehicles (buses and trucks), but vehicles in London don't have to meet that standard. Yet.
The T-Charge is aimed at reducing pollution in the capital. The exhausts of vehicles that don't meet standards of Euro 4 and above emit higher levels of harmful particles and gases. By charging motorists that drive older, more polluting vehicles, the mayor hopes to encourage them to improve their vehicle's emission standards.
'Road traffic is the main source of toxic nitrogen dioxide in London, while pre-Euro 5 diesels contribute significantly to particulate-matter pollution,' says Roy Harrison OBE, Editor-in-Chief of Climate and Atmospheric Science and professor at the University of Birmingham.
He argues removing older diesel vehicles, in particular, from central London will have a positive impact on air quality.
'Diesel vehicles are a much larger emitter of oxides of nitrogen than petrol or electric vehicles,' explains Roy. 'Removing the older diesels from central London would reduce both particulate-matter and nitrogen-dioxide pollution.'
A 2015 study by scientists at King's College London discovered the lives of nearly 9,500 Londoners were shortened each year due to air pollution.
'Exposure to airborne particulate matter is associated with increased risk of heart and lung disease and a reduced life expectancy,' Roy says. 'More people die on high-pollution days than low-pollution days and life expectancy is shorter in highly polluted cities.
'The effects of nitrogen-dioxide pollution are less well defined, but appear to be primarily on the respiratory system. There is clear evidence from California that exposure to high concentrations of nitrogen dioxide leads to a reduction in lung growth in children, which will have lifelong ramifications on their health.'
The charge is £10 per day - for a motorist who drives into London every day, that quickly becomes £300 a month.
Many critics acknowledge pollution in London needs to be tackled, but argue that the T-Charge is negatively impacting motorists who already have financial constraints.
'A lot of our members live in London and are not against measures to improve air quality - they just don't want to be the ones disproportionally bearing the brunt of this cost,' says Denise Beedell, development manager, Greater London Federation of Small Businesses (@fsb_policy).
'The cost of doing business in London is astonishingly high and, for a business that comes in five days a week, the T-Charge is £50 extra on what they already pay,' she continues. 'The T-Charge won't necessarily force any business to close, but these costs keep adding up - eventually, they'll be the straw that breaks the camel's back.
'Small businesses are the bedrock of our community. The owners often live nearby, train up young people from the area and spend the money they earn in the local economy.'
First time T-Charge offenders aren't let off with a warning, which Denise says would have eased the burden.
Phil Blamire is one motorist who received a fine.
'I was sent a letter giving me 30 days to either sell my Land Rover or modify the exhaust, which would have cost £3,000,' says Phil. 'Within that 30-day period, I received another letter saying I had been spotted on the A316, fining me £250. I appealed, but it took months before they upheld my appeal.'
The modification cost was too much for Phil and he had to sell on his limited-edition Land Rover, despite his personal attachment to it.
'It was a special car and I spent a lot of money restoring it,' says Phil. 'I had to sell the vehicle on at a loss, and I've since spotted it on a classic-car site at nearly three times the price!'
Phil points out that part of the problem is that, in the early 2000s, the government was encouraging people to buy diesel cars.
Denise adds that, with new vehicle emission legislation on the horizon, many don't see the point of upgrading their current vehicle to Euro 4 standards.
'A lot of business owners can't afford to upgrade, so they feel they have to just pay the charge and drive into London anyway,' says Denise. 'They don't want to commit to the T-Charge, as they will have to change their vehicle again.' [for the Ultra Low Emission Zone].'
The levels of particulates and nitrogen oxides in the air in central London have dropped since then, according to visualisations from London Air. But there are questions around whether improvements in car technology have had a larger impact in this drop.
If the T-Charge manages something similar, then air quality should improve. However, as Denise points out, many motorists don't have the finances to react to the change in legislation.
Most agree that the T-Charge is a step in the right direction, but that more needs to be done about London air pollution. However, as this is likely to happen, some motorists will hold on to their older vehicles until then.