In general, that is not the law, nor is that common IRD practice, as the many, many, many kiwis who spend time in Australia could tell you. At a guess, your ex

In general, that is not the law, nor is that common IRD practice, as the many, many, many kiwis who spend time in Australia could tell you. At a guess, your ex's family managed to stay resident in NZ (or the IRD may have incorrectly believed them to be so), or they spent too much time in NZ, or didn't spend enough time in the US, or the IRD just screwed up the paperwork, etc. But the law is quite clear, and is explained in detail on the IRD's website: http://www.ird.govt.nz/international/residency/dta/double-tax-agreements-index.html http://www.ird.govt.nz/international/residency/dta/double-ta...