The FBI suggested that it’s complicated to provide the document, and that they would continue to work with House Republicans on the issue. But it does not appear that they are denying that the document exists, even if we don’t know exactly what it says.
According to Fox News:
The FBI did not comply with the House Oversight Committee’s subpoena compelling the production of an FBI document that a whistleblower alleged describes as a criminal scheme involving then-Vice President Joe Biden and a foreign national and relating to the exchange of money for policy decisions.
House Oversight Committee Chairman James Comer, R-Ky., subpoenaed the FBI for the document, which is an FBI-generated FD-1023 form after a whistleblower alleged that the FBI and Justice Department were in possession of it and claimed it detailed an “alleged criminal scheme involving then-Vice President Biden and a foreign national relating to the exchange of money for policy decisions.”
They said the whistleblower alleged the document “includes a precise description of how the alleged criminal scheme was employed as well as its purpose.”