For the first couple of years in NZ I continued to work for my Canadian employer (I'm a lecturer and was teaching online). Once NZ became my tax residence, my Canadian employer dropped their witholding rate to 25%. As a result I owed the IRD the difference between the 25% and my NZ taxation band. Ouch!
I might have been able to get away with it...but I am honestAnd a believe in karma!