The Service and Food Workers Union says it will fight another legal challenge to the right of disability support staff to get the minimum wage for every hour spent on overnight shifts.
The Court of Appeal last month ruled that staff had that right.
The Service and Food Workers Union, which took the case, says the IHC filed a submission with the Supreme Court on Wednesday for leave to appeal against the decision.
Union national secretary John Ryall says the Government is to blame for the development because it is the IHC's main funder and is refusing to pay workers what is owed.
He says that is forcing the IHC to embark on another legal battle.
Mr Ryall says the union plans to file papers asking the court to prevent any further appeal.