The Treasury and HMRC are among 21 public sector organisations being asked by MPs to reveal details of any contracts handed to Fujitsu after the Post Office computer system scandal.
The Commons Treasury Committee says it wants to discover the extent to which taxpayers' money has been spent on contracts with the company since 2019.
That is when the High Court ruled prosecutions were wrongly brought based on Fujitsu's faulty Horizon IT system.
Fujitsu has apologised for its role.
The company has also said it will not bid for further government contracts until the public inquiry into the scandal is complete.
One estimate has suggested that Fujitsu secured more than £4bn of business from the government in the last five years, even after information about the defects involving Horizon emerged.
The Treasury Committee's letter has also been sent to the Royal Mint, the Bank of England, the Crown Estate and the Financial Conduct Authority.
The MPs are seeking details about any contracts awarded to Fujitsu Services Limited or other Fujitsu Global-owned entities.
"There is public concern about the extent to which they are used as the government supplier," Harriett Baldwin, who chairs the Treasury Committee, told OceanNewsUK on Saturday.
Ms Baldwin told the OceanNewsUK earlier that the public outcry was entirely justified, adding that she spoke for the whole Committee "when I express my horror at the injustices the victims faced" and said Fujitsu had questions to answer.
She said: "I think it's important we can see the extent to which taxpayer money has been spent with Fujitsu since the High Court ruling as they are simultaneously assessed on their fitness to remain a government supplier."
Between 1999 and 2015, the Post Office privately prosecuted hundreds of sub-postmasters and postmistresses based on the Horizon system, which had produced faulty accounts. Victims were wrongly accused of offences including theft, fraud and false accounting.
Some went to prison and others have died without being able to seek justice.
Only 93 wrongful convictions have so far been overturned, while thousands are still waiting for compensation settlements more than 20 years on.
The government this month announced plans to exonerate and compensate victims of the scandal, following an ITV drama on the subject which sparked widespread public outrage.
The letter, which calls for a reply within a fortnight, asks about the value of any contracts, whether they were awarded through open competition, if the issues with the Horizon system were taken into account, and what monitoring of Fujitsu's performance was in place.
Questions also include whether the contracts went through a tendering process, the extent to which the company's role in the scandal was considered as part of the due diligence process and whether they considered terminating contracts with the company at any stage.
The UK government continued to award billions of pounds worth of public contracts to Fujitsu even after information about the scandal involving Horizon emerged.
But Cabinet Office Minister Alex Burghart has said the technology firm had written to his department to say that it would not bid for public contracts while the public inquiry was ongoing.
On Friday, the boss of Fujitsu's European arm, Paul Patterson, told the inquiry the company had "clearly let society down, and the sub-postmasters down".
The company has said it has a "moral obligation" to help compensate victims.
