PFA Scotland insist Hearts' players will proceed with their complaint to the Scottish Premier League should their December salaries fail to arrive on time.
On Thursday Hearts announced their players had received their November salaries - 29 days late and with Friday the next scheduled payment date. PFA Scotland held discussions with the first-team squad earlier in the day and the players signed a letter of permission allowing the union to represent them in their battle to recover their owed salaries.
PFA Scotland chief executive Fraser Wishart welcomed the announcement from Hearts, but added in a statement on pfascotland.co.uk: "It is welcome news that the players have received part of the monies outstanding to them. Throughout this whole process they have been thoroughly professional and focused in their outlook."
He continued: "The members have however mandated that should they not be paid fully up to date by tomorrow (December 16) a collective complaint to the Scottish Premier League will still to be lodged.
"It is our hope that the salaries will be paid fully and no further action is necessary."
If the letter of complaint signed by the Hearts squad is presented by PFA Scotland to the SPL on Friday, the situation would likely be placed on the agenda at Monday's SPL board meeting.
PFA Scotland are working with accredited law specialist Margaret Gribbon of Bridge Litigation in the dispute, while access to the legal team of the global players' union, FIFPro, is also available, if required.
Prior to Hearts' declaration that November's payment had been made, Wishart revealed that the move had the "full backing of the dressing room" and was designed to reclaim owed wages.
Speaking to awaiting television reporters, he added: "The players want Hearts to survive and flourish, to get to January so they have the opportunity to sell players."