Write off bad debts: if you have debtors, that have been previously recognised as income, that you now know are not collectible, writing them off will enable a deduction to be recognised.
Consider pre-paying some expenses: If cashflow allows, prepaying some expenses like rent, insurance and office supplies for a period of up to twelve months provides an immediate deduction.
Review inventory: a physical stocktake should be conducted to quantify and value inventory. Slow moving, damaged and obsolete stock must be written off prior to 30 June to claim a tax deduction.
Pay superannuation: SGC for employees must be paid before 30 June 2018 to receive a tax deduction for the business in the 2018 year.
Below is an ATO link regarding general tax planning and strategies to avoid getting in trouble with the ATO: