McDonald’s has said it will begin the process of calculating the amount it owes around 40,000 workers who received the wrong holiday pay for the past 10 years.

The fast food giant was one of several large businesses, including NZ Post, that was found to be noncompliant with the Holidays Act 2003 in a 2016 audit by the Ministry of Business, Innovation and Enterprise .

The company entered into an enforceable agreement with the Ministry regarding annual leave remediation and has been working with them for the past several years to agree on a methodology to calculate the backpayments. It also consulted with Unite Union, which represents around 7 per cent of its workers.

“We have spent tens of thousands of hours working on what is a hugely complex project, in order to ensure the approach to making calculations is correct,” a McDonald’s spokesperson told Inside Retail New Zealand.

“With the agreement in place we can now start the process of doing individual calculations.”

McDonald’s estimates that it underpaid 40,000 workers over the past 10 years, but has declined to provide an estimate of the total underpayment amount.

Unite Union’s national director Mike Treen told the NZ Herald that his estimate was $45-90 million, though he didn’t clarify how he reached this figure.

McDonald’s spokesperson said the company will advertise when it has worked through the calculations and will share a website current and former employees can find out what they are owed.