The majority of Sheffield Wednesday's first-team players were not paid on time for the third month this year, Sky Sports News understands.
The Championship club wrote to players and staff on Monday afternoon to offer their "sincere apologies" for failing to pay them on time.
On Tuesday July 1, unpaid players will have the option to give notice of their intent to terminate their contracts and become free agents.
Wednesday have pledged to fulfil all outstanding payments but have provided no guarantee as to when these payments will be met.
One source has told Sky Sports News that the club are aiming to complete these outstanding payments in the next fortnight.
Sheffield Wednesday declined to comment when contacted by Sky Sports News.
