The force launched an investigation into the so-called ‘partygate’ scandal in January, over 12 events which may have broken coronavirus restrictions in 2020 and 2021.
The 20 fixed penalty notices will be referred to the ACRO Criminal Records Office, which will then be responsible for issuing the fines.
It added that more referrals may be made in the future.
In a statement, Scotland Yard said: “The investigation into allegations of breaches of COVID-19 regulations in Whitehall and Downing Street has now progressed to the point where the first referrals for fixed penalty notices (FPN) will be made to ACRO Criminal Records Office.
“We will today initially begin to refer 20 fixed penalty notices to be issued for breaches of Covid-19 regulations. The ACRO Criminal Records Office will then be responsible for issuing the FPNs to the individual following the referrals from the MPS.
“We are making every effort to progress this investigation at speed and have completed a number of assessments. However due to the significant amount of investigative material that remains to be assessed, further referrals may be made to ACRO if the evidential threshold is made.”
The force said it will not confirm how many people will receive fines, or their identities.
It said: “As it has for all fixed penalty notices issued during the pandemic, the MPS will follow the College of Policing Approved Professional Practice for Media Relations which states that “Identities of people dealt with by cautions, speeding fines and other fixed penalties – out-of-court disposals – should not be released or confirmed.”
“We will not confirm the number of referrals from each individual event subject to our investigation as providing a breakdown at this point may lead to identification of the individuals.”
However, Downing Street will confirm if the Prime Minister is issued with a fixed penalty notice, but it is not expected to confirm the identities of more junior members of staff who are hit with fines.
A fixed penalty notice does not amount to a criminal conviction, but it can result in court summons and criminal prosecution if it is not paid.
Downing Street and Whitehall staff questioned
Around 100 Downing Street and Whitehall staff members were asked by the Met to fill out questionnaires as part of the investigation, named Operation Hillman.
The force made clear that the document had formal legal status and must be answered honestly.
Prime Minister Boris Johnson received a questionnaire on 11 February and it is believed that he attended six of the events under investigation.
However, it is unclear whether he has been issued with a fine.
The Met confirmed last week that officers had started interviewing key witnesses in relation to the questionnaire responses.
The 12 events under investigation took place over eight different dates, including a ‘bring your own booze’ party held in the Downing Street garden on 20 May 2020.
Around 100 staff members were invited to the gathering, organised by the Prime Minister’s principal private secretary Martin Reynolds, at a time when the British public were banned from meeting more than one person outside of their household in an outdoor public space.
Another event includes a surprise birthday gathering for Mr Johnson in the cabinet room in June 2020.