I wouldn't leave it until 31 March. My fund said I needed to prepay by March 29 to get the old rate. I prepaid today until March 31 2018 which was as far ahead as they allow. In the past I was able to prepay 15 months but they seem to have tightened up the software now.
When I looked into this three years back (and changing providers etc) I was told there is supposed to be a statutory limit of paying 13 months on top of the
EXISTING policy expiry date.
Not 13 months from the date of payment which may be confusing some.
Why a 'statutory' limit? Because of the Fed Govt subsidy.
Now the slightly complicated part....
So you have to pay before March 31 (always aim a few days earlier if possible just to be on the safe side) but your current policy expiry may be July 27th.
So your renewal at the current premium price will (paying for 13 months again) take you to fully paid up until August 27th 2018.
The health fund is happy as they have locked you in as a customer for (in this case) 17 months into the future and you have paid 5 months in advance of the date you needed to. So the health fund gets to use your money for the extra 5 months, gets the Govt co-pay 5 months earlier as well and knows it is not going to lose you as a customer in the next financial year.
The reality is you are not really SAVING the premium increase - merely postponing when you pay it.
So the premium increase from 2013 I ended up paying in 2014, and 2014's increase I paid in 2015. The true saving to me was the actual interest I earnt on the amount of the premium increase for the delay of 13 months. Add in a little annuity/geometric calculation to account for the seemingly perpetual nature of this and you find that apart from a warm inner glow - you've made a little not a lot.
You make the most if you are paying off a home mortgage and leave all excess funds in a set-off account. If you are not organised enough then the amount you make by delaying the annual days of reckoning is significantly less.
... but as a $ in my pocket is significantly better than in some CEO's - I play the game.
Now to convince the call center operator to accept those $100 CMCs.