Motorists in central London are to be given an extra day to pay the congestion charge.
Drivers must pay up by midnight, or face a £100 fine
People driving into London must pay the £8 charge by midnight, or face a £100 fine, reduced to £50 on prompt payment.
But from 19 June they can pay £8 by midnight, or £10 by midnight the next day, mayor Ken Livingstone said.
He also indicated that he favoured a £20 charge for people driving high-polluting cars, in an effort to reduce CO2 emissions.
Of the decision to give drivers the chance to pay the next day, he said: "This change will give people an extra day to pay. If they forget to pay on the day they now have an extra day to avoid receiving a penalty charge."
BBC correspondent Jo Coburn said it followed quite a few complaints from people who said the midnight deadline did not give them long enough to pay.
The move was backed by business organisations, who had raised concerns about the deadline.
Baroness Jo Valentine, chief executive of London First, said: "Surveys of our members have consistently shown that next day payment is a must and we welcome this move to reduce the hassle factor of the scheme."
The move was backed by the London Assembly Transport Committee, with some reservations.
Chairman Geoff Pope said: "Too many people were caught out because they simply forget to do it the same day.
"But an even fairer system would allow drivers to pay the basic daily rate the following day. Surely it is not rocket science to implement such a system."