MPs have earned £17.1m on top of their salaries in this parliament, with around two-thirds of the money going to just 20 MPs.
Westminster Accounts, a joint project between Sky News and Tortoise Media to shine a light on how money works in politics, found the majority of the extra earnings (£15.2m) went to Tory politicians, while Labour MPs earned an additional £1.2m.
Former prime minister Theresa May received the most on the list, earning £2,550,876 since the session began in December 2019.
Her single biggest pay cheque came from Cambridge Speaker Series, who gave her £408,200 for six talks in California, as well as flights and accommodation for her and a member of staff.
Mrs May was able to earn £38,000 from MPSF for a talk she gave virtually.
Meanwhile, Labour's shadow foreign secretary David Lammy topped his party's list with additional earnings of £202,599.
The debate over second jobs dominated 2021 after former Tory MP Owen Paterson became embroiled in a lobbying scandal that eventually led to his resignation.
All MPs are paid a base salary of £84,144.
Search for your MP using the Westminster Accounts tool