Liverpool are still owed £25m by Barcelona for playmaker Philippe Coutinho, according to a report.
The Reds reluctantly sold the Brazil international to Barca for a fee rising to £142m in January 2018, making him the third most expensive player of all time.
Only around £105m of that was handed over upfront, though, with the rest to be paid in instalments, as agreed by Liverpool at the time.
Spanish outlet El Confidencial claims that Liverpool have been paid a further £12m in the three years since that high-profile transfer, leaving a large amount outstanding.
The same report suggests that the Premier League champions are not alone in being owed money by Barca.
Bordeaux are said to be awaiting an £8.8m payment for winger Malcom, while Gremio and Ajax are due £7m and £14m respectively for Arthur and Frenkie de Jong.