Generally, splitting income of a couple is allowed only if you can justify the amount paid to the smaller income earner.
If you work for yourself, you'll need to get the Inland Revenue's approval before paying your spouse or partner. This need for approval does not apply to companies. All that is needed is for you to be able to justify the income if IRD asks.
The rules for couples who are partners in business are a little more complicated. Please ask us if you want to know what they are.
Where the couple are both working fulltime in a company, the usual rule is you can pay them as much as you like. However, we think excessive salaries to a low skilled partner could upset IRD. The department can also be upset by excessively low salaries, particularly if they result in lowering the overall tax paid.