Downing Street is seeking to cancel a county court judgment against Prime Minister Boris Johnson that cites an unpaid bill of £535.
A Downing Street spokesperson said the claim against the PM was without merit.
Anyone who has had a county court judgment (CCJ) against them can apply for it to be cancelled - or "set aside" in the legal language - but they must convince the court that there is a good reason for this to happen.
That could include the judgment having been issued in error - perhaps because the debt had actually been paid, or because there was never a debt in the first place.
It's not clear whether that is Mr Johnson's argument, given he could have raised these points before the court order was issued.
Sometimes, people seek to have a CCJ cancelled because they genuinely did not know about it, such as if they never received the formal request to tell the court their side of the story.
That can happen when the court has been provided with the wrong address for a debtor who only later learns of the judgment when they discover it has damaged their credit score.
The official rules for applications to set aside a judgment state: "Most applications will require a hearing and you will be expected to attend. The court will allocate a hearing date and time for the application. Please indicate in a covering letter any dates that you are unavailable within the next six weeks."
The application must come with some kind of "statement of truth", explaining why the judgment should be set aside.
The prime minister could * instruct a lawyer to appear for him.