If the oligarch does insist on that money being returned, it could throw the sale of the club into chaos.
Abramovich originally claimed he would write off the debt, when announcing his decision to sell the club in March. Since then, he has been placed under sanction by UK Government, who have frozen his assets, including Chelsea.
The Russian instructed US merchant bank, Raine Group, to find buyers, with the Treasury set to issue a special licence to push through the sale.
That process is close to completion, with Todd Boehly named as the preferred bidder.
Sir Jim Ratcliffe is still hoping to hijack that deal, but Boehly is in a period of five days exclusive negotiations.
Bidders have already had to meet ever-changing demands from Raine, including the guarantee of £1bn investment in the club on top of the sale price.
They have also had to offer assurances they will not sell the club for at least 10 years.
Last week there was a fresh demand for an extra £500million just before Raine chose their preferred bidder.
The sale was already seen as incredibly complex, which was only made more difficult due to the speed with which it had to be conducted, with club operating under a special licence following sanctions placed on Abramovich. Late demands have complicated it further.
There is no official confirmation that Abramovich will ask for his debt to be repaid, but that is the fear within Government and they are adamant that no monies will be allowed to go to a sanctioned individual.