IHC spokewoman Philippa Sellens said it had no choice but to appeal the recent court ruling which stated that staff who slept over at IHC premises while caring for clients would have to be paid the minimum wage of $12.50 an hour.
"We have no money to pay what it would cost us to cover this," she told the New Zealand Herald.
Night staff are currently paid $34 a night for eight to 10 hours, so payment can be as low as $3.40 an hour.
The Service and Food Workers Union, which took the case to the court, said it had some sympathy for the IHC and it was time for the Government to get involved.
Workers have the right to claim up to six years' backpay.
The IHC's Idea Services has about 6500 carers who look after about 3500 clients in community-based care.
Figures supplied to the Employment Court showed it would cost IHC about $80 million in backpay and about $20 million a year extra in wages.
The case may have implications for other employees, such as those who look after the elderly.
IHC was looking to the Ministry of Health, its primary funder, for a solution.
Health Minister Tony Ryall said Crown Law was considering whether the ministry should join the IHC in seeking leave to take the decision to the Court of Appeal.
Union secretary John Ryall said "a whole lot of chickens are coming home to roost".
"This is a case that has been sitting around for some time which the union has picked up and taken," he said.
"But it is essentially an issue that needs to be sheeted back to the Government."
