HMRC is contesting the outcome of a tribunal which saw oldco Rangers win an appeal in principle against a bill over the use of Employment Benefit Trusts (EBTs) from 2001 to 2010. The tribunal stated that the "controversial monies received by the employees were not paid to them as their absolute entitlement".
A spokesman for HMRC said: "HMRC will seek permission to appeal the tribunal decision."
Rangers argued that the payments, thought to be close to £49million, were loans rather than wages and not subject to tax. The oldco was consigned to liquidation in June after it failed to exit administration via a company voluntary arrangement.
Rangers will in February travel to Clydesdale Bank Premier League opposition for the first time since, but without support after chief executive Charles Green backed supporters' plans to boycott the Scottish Cup fifth-round tie at Tannadice.
Rangers were on Monday drawn to play at United, with supporters' groups immediately calling for a stay-away protest for the first match at SPL opposition since they were relaunched as a new company and denied entry to the top flight.
In a statement, Green said: "This is a unanimous decision by the board, senior management and staff at Ibrox. Everyone at this club is dismayed at the actions of certain SPL clubs, which were actively engaged in trying to harm Rangers when we were in a perilous situation and we are acutely aware of their attitude to us.
"Feelings remain very raw and it should be no surprise that we as a club feel this way. It is unsurprising too that there has been a reaction from our supporters to this particular fixture.
"The last thing we as a club want to do is to compromise security arrangements for any match. I therefore appeal to all fans not to travel to this match and to Dundee United not to sell tickets to Rangers supporters."
United, who beat Rangers twice in three years in the competition before they were consigned to liquidation, refused to comment on early reports of a possible fans' boycott, with some Rangers fans believing Stephen Thompson, the chairman at Tannadice, was an influential figure in their demotion to the Irn-Bru Third Division.