David Cameron reportedly made over £7million from Greensill Capital before the company collapsed in March.
The former Prime Minister was revealed to have made £3.25 million after cashing in shares from the company in 2019, and a salary of roughly £700,000 a year for work as a part-time adviser.
The BBC's Panorama programme is believed to have obtained a letter between the firm and the former prime minister detailing the value of his shares.
Mr Cameron is believed to have made approximately £7.2million before tax from Greensill over a two-and-a-half year period.
The firm collapsed in March this year, after its leading insurer, Tokio Marine, walked away.
Mr Cameron's role at Greensill then came under the spotlight for his approaches to ministers and former colleagues on behalf of the company, which has put it at the heart of a lobbying row.
MPs had said Mr Cameron showed a 'significant lack of judgment', though he was cleared of breaking lobbying laws.
His spokesman said the former PM's finances were a private matter, according to the BBC.
It was earlier reported that Mr Cameron had been paid the equivalent of £29,000 per day for his advisor role after the Financial Times revealed he was only contracted to work 25 days a year.
And when he appeared in front of MPs on a select committee in May, Mr Cameron was markedly coy about how much he had earned.
He said he had been paid 'a generous annual amount - far more than what I earned as prime minister'.
Mr Cameron joined Greensill in August 2018. The former politician went on a behind-the-scenes lobbying blitz at the start of the pandemic as the company sought access to a £200million state-backed Covid lending scheme.
Official records revealed that between March and June last year he sent 62 text messages and WhatsApps to Chancellor Rishi Sunak, former friend Michael Gove and other ministers as well as top civil servants and a deputy governor of the Bank of England.
But Mr Cameron insisted it had not been 'some giant fraud' and that Greensill had had a 'really good idea' for how the Government could help businesses in the pandemic.
When asked whether he had lucrative share options in Greensill, Mr Cameron told the select committee he had 'shares, not share options'.
He added that reports he had share options worth £60million were 'completely absurd'.