Your PIR is based on your taxable income in the last two tax years i.e. years ended 31 March. You should elect the 10.5% rate if:
Your gross taxable income in either of the last two years was less than $48,000,
You should elect the 17.5% rate if:
Your gross taxable income plus your PIE allocated income was between $48,001 to $70,000.
Your gross taxable income includes your wages, interest, rents etc.
If your income is over these limits then your tax rate is 28%.