Hi Gem,
Also due in sept
you legally have to give a minimum of 3 months notice to your employer (before your EDD) by written notice so you probably need to get onto it now.
You can apply for the whole 12 months and come back earlier provided you give them 21 days notice, if you apply for a shorter period and want to extend your employer can refuse to do so.
When you use your leave is up to you - according to the IRD forms, the latest you can start PPL is your EDD, the earliest is 36 weeks, so you can choose to finish up earlier, some people cut down their hours in the final weeks and use A/L that way.
The only thing to remember is that outstanding leave (leave earnt in the previous years) is paid at full value, any accrued leave (leave earnt in this year) is paid out at your hourly rate of the previous 12 months - so if you take a whole year off, you will still accrue 4 weeks leave while you are away but it is paid out at $0 (as you have earnt nothing in the 12 months you have had off), if you took 6 months off it would be paid at half your hourly rate (as you would have earnt half your yearly earnings by only working 6 months) if that makes sense. Talk to your payroll person about what leave you have, as if needed you can use sick leave for medical reasons too. I have decided to finish up at 37 weeks and use my leave (2 weeks outstanding and 1 week accrued so I get paid for it) and then start my PPL on my EDD.
Your employer may agree to pay out some of your leave too, otherwise ask if you could tack it onto the end of your leave (either the PPL or the extended leave) so that it doesn't lose its value
Hope this helps!