I am not an accountant. So please review with an accountant but here are some immediate ideas for you to discuss before the End of the Year.
1) If possible, hold off depositing monies till July. This often pushes the tax owing on these to next year.
2) Review the coming expenses some if paid now will give you a deduction now. Commonly done here is to pay a big supplier now.
3) Review your BAD Debts - no point in paying taxes on these debts if you do not have them anymore. Doing this you can claim back on GST credits too. To do this they need to be outstanding for over 12 months or have evidence that they are bad debt, e.g. the debtor is bankrupt. As a written record must be kept, I suggest that you make a dissection called bad debt and issue a credit note to these debtors for the debt. This will adjust your GST and sales ledges in our system. You can also as such adjust it back if by some miracle you do get paid.
4) If you have been working from home due to COVID-19, you may have more expenses you can claim a tax deduction. Better check here as there have been cases here of people overclaiming, e.g. claiming 100% of internet charges for business and none for personal use.