13 Mar 2019 Workers who are paying too much tax because of incorrect secondary tax codes The Taxation (Annual Rates for 2018-19, Modernising Tax are ignored in calculating the tax liability of the consolidated group. There are latter apply, they will generally require the interest rate for the NZ borrower to be Tax codes only apply to individuals. They help your employer or payer work out how much tax to deduct before they pay you. Tax rates are used to work out how much tax you need to pay on your total income for the year, from all sources. Individuals pay progressive tax rates. This means you pay a graduated amount depending on how much income you get.