With the Labour Weekend fast approaching, Public Holidays is still an area that many people get wrong (lets not talk about the Mondayisation Issue), so the bare facts around public holidays are:
If you work on a Public Holiday - everyone (salaried, casuals, permanent, part-time staff) who works on a Public Holiday must be paid at a premium of Time & Half for 'all hours worked'. I put the last part in brackets because, under the legislation, you only need to pay for the actual hours worked at T1/2, so for example, if an employee who normally works 8 hours a day works 2 hours on a Public Holiday, the laws says you only need to pay the 2 hours at T1/2, but in reality this is not practised and most employers will pay the additional 6 hours at an employee Relevant Daily Rate or they are never goinng to get anyone to work on a Public Holiday. If the employees hours cross midnight, then again, only the hours worked on the Public Holiday must be paid at T1/2.
If you work on a Public Holiday and its a Normal Working Day - the Normal Working Day can be determined by a Roster or Work Pattern or determined by your Contract. In these situtaions yuou get paid at T1/2 for all hours worked and you accrue an Alternative Day. I have highlighted Day as many employers accure Hours for Alternative Leave which is legally incorrect and the hours you work on a public holiday have zero impact on the hours you get paid when you take your Alternative Day. For example, if I work 2 hours on a Public Holiday, and it is my Normal Working Day, I get 1 Alternative Leave day accrued (not 2 hours). When it comes to taking my Alternative Leave Day I might request a day that I would normally work 10 hours, if you as the employer agree then you must pay the employee 10 hours (their Relevant Daily Pay) and reduce their Alternative Leave by 1 day.
Another scenario that can materialise around Public Holidays is staff who are 'on call'. If someone is on-call and even if they are not called into work, then you must accrue an Alternative Day for them, as they are deemed not to be in a position to enjoy the day off.
If you do not work on a Public Holiday and it is an otherwise Normal Working Day - in this case you must pay an employee for the day at their Relevenat Daily Pay (if it can be determined) or their Average Daily Pay.
Mondayisation of Public Holidays - is covered really well here - https://employment.govt.nz/leave-and-holidays/public-holidays/mondayisation/