Up to 20 people owed money by the company Spotless should be repaid by the end of the week, the union representing cleaners says.
E Tū said the workers had not been paid for all the hours they had worked in the past few months and hundreds more have also been affected.
The union met Spotless managers today and said part of the problem was the payroll system's voice recognition mechanism.
E Tū assistant national secretary John Ryall said Spotless has also committed to repaying people within 24 hours if there is any future issue.
"They largely took the line that it's the fixing up of the problem that's important.
"From time to time mistakes will occur but they weren't blaming people for that but wanting to make sure that workers who were on quite low incomes would not suffer."