"Microsoft offered to provide technical expertise and assistance," a representative for the company wrote. "The best of our knowledge, no Microsoft employee has provided such services."
The letter did not say whether Microsoft's offers of help were rebuffed by the administration. A spokeswoman from HHS said the department was looking into the issue.
The White House announced the "tech surge" last week in response to ongoing problems with HealthCare.gov, the portal where millions are meant to sign up for health coverage.
Federal health officials have not disclosed which companies are involved in fixing the website apart from the contractors who helped build it.
Oversight also received letters back from travel site Kayak, which said it has had no contact with the administration, and Verizon, which said it is still working to answer the panel's questions.