A tax expert says he's puzzled by what National's promises of new revenue could include.

The party plans to release its tax policy tomorrow morning, alongside four new sources of cash for the Government to splash.

Its' finance spokeswoman promises it won't pressure inflation and needs no additional borrowing.

Dentons Kensington Swan partner Bruce Bernacci says he's looking forward to hearing it.

"The National Party's ruled out wealth taxes, capital gains taxes, inheritance taxes, etc. So in terms of big policy changes, it doesn't leave a lot to work with."

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