New Zealand could have one of the least competitive corporation tax rates - but that could change by May.

The Prime Minister has hinted this year's Budget could make way for relief. 

The rate has stayed on 28 percent since 2011 - but Finance Minister Nicola Willis is making comparisons with countries like Ireland, with a 12.5 percent rate.

Advisory expert Robin Oliver says such a change would have a big impact.

"If we went down to 25, that'll cost us about a billion dollars per annum in tax - and that still wouldn't be much competitive compared to these small, open economies."

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