Real Madrid must reportedly raise €200m (£168.3m) to balance their books for the 2019-20 season and need to generate €100m (£84.2m) simply to avoid a Financial Fair Play punishment.
The Spanish giants splashed around €350m (£294.6m) during a summer spending spree which saw them bring in the likes of Eden Hazard, Luka Jovic, Eder Militao, Ferland Mendy and Rodrygo Goes.
Madrid were able to make €150m (£126.2m) of that back through player sales, but Financial Fair Play rules dictate that the maximum net spend any club can have during a season is £84.2m.
Marca reports that the deficit is likely to have an impact on Los Blancos' transfer plans, with the club expected to focus on selling players rather than bringing new ones in.
President Florentino Perez has not entirely ruled out making signings in January, but the need to raise more than £84m before the end of the campaign could scupper any chances of a big-money move for Manchester United midfielder Paul Pogba.
Madrid have also been credited with an interest in Arsenal striker Pierre-Emerick Aubameyang and Manchester City winger Raheem Sterling, but would need to sell before they buy if either were to join in January.