NSW , Out of a lease they have to give you 60 days in writing notice of a rent increase, and they cannot increase the rent by more than $30 a year and only one increase every 6 months....

So if he wants to put it up $15.00 now, then he needs to give you 60 days notice and then you start paying the extra rent. And then next year he can put it up $15.00 again but only with 60 more days notice.....

but no more than $30 a full year increase if that helps.
also the terms would be written on your lease.
The increase needs to be in writing.

I wouldn't tell him what he has to do, but rather insist they he do it all the right way as per your lease,
if you have a problem you can file with the Tenacy tribunal in NSW and they will sort it out for you

But until he gives you a letter and does the increase properly I would not pay an extra cent. ALSO they have to prove the rent should increase as per market value or properties in the area with the same amenities for rent for a higher price. if you think the rent increase is in fair you can say something, they can't just put up the nt to move with ' the times ' lol

best of luck

PM me if you need anymore help