@ Snoopy - Thanks for the detailed response. I was aware that WBC NZ listed shares carry partial imputation credit (which is why is phrased it as "do not carry full imputation credits). I'm also aware that imputation/franking credits have no value outside NZ/Au respectively. Your reminder that NZ investors want international exposure combined with the partial imputation credits appears to be the missing piece and explains why there hasn't been a steady migration of WBC shares from NZX to ASX – I guess I've been away too long.

@ Snoopy and Bjauck – As a non-resident shareholder, imputation and franking credits do matter to me. If there's no imputation credits (provided via a paper supplemental dividend) on NZ shares I lose 30% to NRWT. The same happens in Australia with franking credits. If I understand correctly, a company must utilise its available imputation credits to pay a supplemental dividend to overseas shareholders to avoid deducting NRWT.

The imputation/franking of dividends is one of the first things I look at when evaluating an investment. This is why, when units in Westpac Trust were swapped out for NZX listed WBC shares I shifted my shares to ASX.

Thanks to you both for taking the time to reply.