The New York attorney general’s office on Thursday took exception to a $175 million bond that Donald J. Trump recently posted in his civil fraud case, questioning the qualifications of the California company that provided it.

The dispute stems from a $454 million judgment Mr. Trump is facing in the case, which the attorney general’s office brought against the former president and his family business.

Mr. Trump was obligated to obtain the bond as a financial guarantee while he appeals the penalty — or else open himself up to the possibility that the attorney general, Letitia James, would collect the judgment. Without a bond in place, Ms. James could have frozen his bank accounts and begun trying to seize some of his New York properties.

Mr. Trump appeared to stave off this calamity on Monday when he posted the $175 million bond. Although he was originally required to secure a guarantee for the full $454 million judgment, an appeals court granted him a break, allowing him to post the smaller bond.

The company providing the bond — which is a legal document, not an actual transfer of money — essentially promises New York’s court system that it would cover $175 million of the judgment against Mr. Trump if he loses his appeal and fails to pay.

Now, however, Ms. James is raising questions about the company that provided the guarantee to Mr. Trump, Knight Specialty Insurance Company, owned by Don Hankey, a billionaire who made his fortune with subprime loans.