@Djc1 it'll be easy to work out why, comparing to previous bills, especially the last period from 12 months prior.
In the past few years in particular, power prices have gone up and up, so too daily supply charges, solar FITs down.
Fed and possibly state power rebates also disappeared a few bills ago.
You don't say of it is monthly or quarterly billing, I'd assume quarterly.
Is it an estimated bill for some reason ?
These can be notoriously high.
Again, I'd assume actual as you likely have a digital meter, if you do have what I'd expect to be at least decent solar, possibly a battery too.
If not an estimated bill, and you really are totally zero usage, solar and battery, the only things I can put this down to would be a change of plan / tariffs, possibly a demand tariff is sneaking in somewhere, or the daily supply charge is what you are seeing.
Highest bill in 10 years leads me to think it is far more than supply charge though, which varies with your state / region DNSP, but even if it was a couple of bucks a day that would still be only $180 or so a quarter, more likely far less.
Maybe review past bills and see what’s changed, if you are getting usage charges . . . you might not be as net zero as you think ?