Nearly 2,000 football agents have been warned they could face tax investigations by HMRC.
Her Majesty's Revenue and Customs have written to intermediaries as part of a new investigation into transfer activity and fees.
The letter, which has been seen by Sky Sports News, states: "We have found a number of issues in relation to fees that are paid to some agents.
"If we suspect that onward payments are made from fees received by an agent we will check all surrounding transactions to establish if there has been any potential facilitation of tax evasion".
HMRC is currently investigating 38 agents and 40 football clubs.
Premier League clubs paid £211m in agent fees during the 2017-18 season, a £37m increase on the previous season.
In 2017 HMRC officials raided offices at Newcastle and West Ham as part of an investigations into tax and national insurance fraud.