Thirty more penalties have been issued as part of Operation Hillman, the investigation into allegations of lockdown-busting parties in Downing Street and Whitehall, police said on Tuesday.
The first partygate fines were issued early in April to 20 partygoers, including Whitehall’s former ethics chief.
This means £20 ($26) or £50 penalties have been issued to at least half of the 100 civil servants under investigation.
Despite repeatedly denying he had broken lockdown laws, Mr Johnson is understood to have been present at six of at least 12 events being investigated.
The fixed penalty notice Mr Johnson will receive relates to the birthday gathering held for him on June 19.
Chancellor of the Exchequer Mr Sunak will also be fined for attending the event. It was a week to forget for the finance minister, whose billionaire wife, Akshata Murty, was forced to alter her non-domicile tax status when it was revealed she did not pay anything to the UK Treasury on her foreign earnings.
Police confirmed the prime minister’s wife, Carrie Johnson, would also be penalised.