New Zealand Aluminium Smelters, the operator of the Tiwai Point smelter, will go to the Supreme Court in a bid to overturn earlier decisions on the payment for statutory holidays that fell on a weekend, which it says leaves it with a $20 million bill and will impose new costs in the future.

The smelter has sought leave to appeal to the country's top court after last month losing its bid to overturn an Employment Court ruling.


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The lower courts ruled that while the relevant employment law doesn't require payment for unworked statutory holidays that fall on a weekend, the smelter's collective agreement with the E Tu union does, and because the smelter moved to 12-hour working days in the 1990s, all such payments should be for 12-hour working days rather than the eight-hour days on which the smelter calculated workers' statutory holiday payments.


"This isn't a decision we have taken lightly," NZAS chief executive Gretta Stephens said in a statement. "I believe it is very important for NZAS to obtain this final legal determination so this can be resolved with certainty for all."

The Appeal Court upheld the earlier decision based on the collective agreement rather than the structure of the legislation, which required shift staff accrue a day in lieu for a statutory holiday as it occurred, irrespective of whether or not the day was worked or taken as a normal weekend day.

If leave for the appeal is granted, the smelter's argument will focus on the interpretation of the Holidays Act. NZAS accepts it's required to accrue a lieu day for every day worked on a holiday, but disagrees employees should get that day if they actually had the public holiday off work.