sbiddle:Last year's IRD system changes have caught out a lot of people who may have had their tax rate too low (whether accidental or intentional) because they had no way to check it was correct, and this has resulted in people having to pay the IRD.
Interest rates being as low as they are you'd be unlucky (or very lucky) to have to pay that much. I had the wrong rate at BNZ but the difference in tax got written off by IRD.