Bonus to KiwiSaver Calculator NZ

This calculator helps you decide whether to pocket a work bonus as cash or direct it into KiwiSaver, by showing what each choice is actually worth over time. Bonuses are taxed as income no matter what you do with them, so the comparison starts from the same after-tax figure rather than the headline amount. You enter your bonus before tax, your marginal tax rate (17.5%, 30%, 33% or 39%), the annual return you expect your KiwiSaver fund to earn, and the number of years until you plan to retire. The calculator works out the tax on the bonus and the net amount you would receive as cash today, then compounds that same net figure at your chosen return over the years you specify to show what it could grow to inside KiwiSaver by retirement, along with the extra growth that represents. Use it to weigh up money in the hand now against a larger, but locked away, sum years down the track, whether you are deciding what to do with an annual bonus or any lump sum you do not need soon. Keep in mind that KiwiSaver money cannot be accessed until age 65 or a first home purchase, and the growth shown assumes a steady return rather than the ups and downs of real investment markets, so treat the result as an indicative estimate rather than financial advice.

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$15,022
what the bonus could grow to in KiwiSaver by retirement
Net bonus as cash now$3,500
Tax on the bonus$1,500
Growth in KiwiSaver$11,522

A bonus is taxed as income whether you take it or contribute it, so this compares the same after-tax amount. KiwiSaver growth assumes a steady return and is not guaranteed, and the money is locked until 65 or a first home. Estimate only, not financial advice.

How it works

The calculator works out your after-tax bonus by applying your tax rate, which is what you would receive as cash. It then grows that same net amount at your KiwiSaver return over the years to retirement, to show what it could become if contributed instead. The difference is the growth you give up by spending it now, set against the flexibility of having the cash available.

Worked example

A $5,000 bonus taxed at 30% nets $3,500 as cash. Contributed to KiwiSaver and grown at 6% for 25 years, that $3,500 could become around $15,000. The trade-off is that the KiwiSaver money is locked away until retirement or a first home.

Related calculators

Data sources: the rates and thresholds on this page are maintained against Inland Revenue. Figures are checked twice monthly.

Frequently asked questions

Should I put my bonus into KiwiSaver?

A bonus is taxed as income either way. Putting the net amount into KiwiSaver lets it grow until retirement or a first home, but it is locked away. Taking it as cash keeps it accessible. The calculator compares the long-term growth against the cash today.

Is a bonus taxed if I put it in KiwiSaver?

Yes, a bonus is taxed as income, so this compares the after-tax bonus taken as cash with the same after-tax amount contributed to KiwiSaver and grown over time.

What is the catch with KiwiSaver?

KiwiSaver is locked until 65 or a first home, so the growth comes at the cost of access. If you might need the money sooner, that flexibility has real value.