International Desk: Lancashire Police said it had issued a 42-year-old man from London with a conditional offer of a fixed penalty.
No 10 said Mr Sunak “fully accepts this was a mistake and has apologised”, adding that he would pay the fine.
Passengers caught failing to wear a seat belt when one is available can be fined £100.
This can increase to £500 if the case goes to court.
The prime minister was in Lancashire when the video was filmed, during a trip across the north of England.
The video – to promote the government’s latest round of “levelling up” spending – was posted on Mr Sunak’s Instagram account.
