Investing in a portfolio investment entity (PIE) could affect your other Inland Revenue responsibilities. It's less likely to have an effect if the income is from a locked-in PIE (KiwiSaver, retirement saving scheme or superannuation fund).
Income from a locked-in PIE will not affect your Working for Families Tax Credits or your student loan repayment obligations.
Income from a non-locked-in PIE will affect your Working for Families Tax Credits entitlements and student loan repayment and should be included in the Adjust your income - IR215 form.