Income Tax is the percentage of your income that is collected by the tax department. Personal income tax is payable at the time the income is earned, and when you work in Australia your employer should deduct tax at source at the required rate. If you have paid too much tax (or too little!) you should file an income tax return. The tax year ends June 31 every year in Australia. Internex is not a registered tax agent and cannot give advice on tax however all information you require is available at http://www.ird.govt.nz/income-tax-individual/ or https://www.ato.gov.au