PFA Scotland is set to hold talks with Hearts' players over the coming days after they failed to receive their monthly salaries on Wednesday.
The Edinburgh club have told senior squad members they will be paid at the "earliest opportunity" following a second consecutive month of overdue wages.
Hearts admit they are currently trying to "obtain funding" in order to make those payments after settling a tax bill of more than £1million with HM Revenue and Customs on Tuesday.
But the players` union wants a definitive date as to when their members can expect to receive their wages, and PFA Scotland chief executive Fraser Wishart said: "We are disappointed that once again our members' wages have not been paid on time.
"I wrote last month to the club asking for an undertaking that they would take steps to ensure that this would not be repeated. The fact that the wages were three weeks late last month caused many players some financial problems.
"Once again there will be an expectation that our members will simply turn up to train and play without any certainty as to when they will be paid. I have therefore emailed the club today (Wednesday) to once again ask for a definitive undertaking as to when the wages will be paid.
We will be in discussions on this matter with our members in coming days. Our members are only too aware of the various legal options open to them as they have had to suffer this previously. The players have shown a great deal of patience in recent times and PFA Scotland is ready to follow their instructions at short notice."
Senior squad members had to wait 19 days for last month's overdue wages, which were eventually paid on November 4. Players were persuaded 24 hours earlier not to make a formal complaint to the Scottish Premier League by manager Paulo Sergio but now face a delay again this month.
A club spokesperson said: "We expect salaries to be paid into the senior players' accounts at the earliest opportunity and have informed the players of this today (Wednesday]. The club is experiencing an income shortfall due to lower than expected transfer monies. Our future funding is secure but requires time to be organised.
"The club also unfortunately failed to reach agreement with HMRC which would have allowed it time to pay a tax bill in excess of £1million, that was settled in full yesterday (Tuesday). As such we are currently looking at options to identify new income opportunities and obtain funding for the players' salaries."
Source: PA
