Championship promotion-chasers Sheffield United have been placed under a transfer embargo by the English Football League.
The move relates to a breach of rule 52.2.3, which concerns the default of payments to another club.
The EFL has not specified which club or player the matter relates to.
However, the move means the Blades cannot register a player “without the written prior consent of the league” until the overdue payment is made.
Sheffield United are second in the Championship, five points behind leaders Burnley but 11 ahead of third-placed Watford.
They still receive parachute payments following their relegation from the Premier League in 2021.
In their most recent financial statement, to June 2021, published on 5 April 2022, Sheffield United owed £18.25m in outstanding transfer payments, with £2.49m owed to the club.
The club’s owner Prince Abdullah has been in talks with an unnamed buyer over a potential takeover, which manager Paul Heckingbottom said had been impacting on their January transfer plans.