Southend have been contacted by the Professional Footballers' Association after failing to pay February wages to staff on time, BBC Essex reports.
Salaries at the League One club, who are under a transfer embargo because of an unpaid tax bill, were due on Friday.
The Shrimpers will owe £668,000 to HM Revenue and Customs by 11 March, with a further month "stacked up behind".
The PFA held a meeting with Southend players in January after staff and some coaches were not paid on time.
As a result of the late December payment, the club face an English Football League disciplinary hearing for failing to adhere to the terms of the players' contracts.
If found guilty, potential punishments include a fine, points deduction or even withdrawal of their league membership.
Sol Campbell's side are 22nd in League One, 17 points from safety.