Up to 10,000 drivers who did not pay the £5 congestion charge on its first day of operation on Monday will be chased up to pay their fines.
Parts of London were deserted on Monday
London Mayor Ken Livingstone said the £80 penalties would start landing on people's doorsteps by the end of the week.
"We're not going to allow a few free-loaders to ride on the back of hundreds of thousands of law-abiding Londoners," he said.
Mr Livingstone hailed the first day of the charge as a success beyond his expectations and said 100,000 drivers had paid the fee.
The scheme's first day saw a 25% reduction in traffic in central London, partly due to the half-term school holiday.
We're not going to betray those Londoners who cooperated yesterday to produce the best day in traffic flow we've had in living memory
Ken Livingstone, London Mayor
Drivers who do not pay £5 before 2200 GMT on the day they travel, or £10 before midnight, are liable for an £80 penalty, or £40 if they pay within 14 days.
The initial figure of 10,000 non-payers could fall as the photos will be checked manually before any fines are issued.
Speaking at a press conference on Tuesday, Mr Livingstone said: "Yesterday was much more successful than was expected.
"None of the problems we feared of gridlock on inner ring roads and the collapse of the call centres materialised.
"Considering this is one of the largest IT schemes in Britain, it was a remarkably smooth-running day."
Many of the non-payers were probably "chancers" who hoped the system would suffer a technical meltdown on its first day to help them evade the charge, he added.
But shadow transport secretary Tim Collins said Mr Livingstone could not be happy that so many people had not paid - even if he was counting on getting £80 fines from each of them.
"Making a profit out of inefficiency is of dubious legitimacy on day one - it would be a major public scandal if it continues into the future," he said.
A total of 190,000 vehicles were thought to have entered the charging area, 25% less than on a typical weekday.
Between 15,000 to 20,000 were fleet vehicles which had also paid through fleet arrangements.
How drivers paid
40% at retailers
30% on the phone
10% by text
Some 45,000 vehicles, such as buses, taxis and emergency vehicles, were exempt from the charge.
In a year, London is expected to make £130m from the charge, including £90m for improving bus services and £4m for creating safe walking routes to schools.
He said the scheme could extend westwards to cover other parts of Westminster and Kensington, if voters allowed it in the next election.
A motoring organisation said average speeds had increased from 10 miles an hour to 20, although Mr Livingstone said this would not be maintained.
He brought forward his date for a full assessment and "firm judgements" of the scheme's success to before Easter.
Monday also saw 300 new buses on the capital's streets to help meet the expected rise in demand for public transport.
A London Underground spokesman said Tube trains were no busier than normal on both days.
TfL managing director Derek Turner said: "It's not totally introduced yet, we still have a school holiday period on, there could be further teething problems and adjustments to be made."
The AA warned reduced traffic in central London could impact on the capital's economy.
Freight companies oppose the charge and before their annual Freight Summit on Tuesday, some representatives said the arrangements for delivery firms to pay were chaotic.