Just put in your income into the textbox below and then click anywhere on the form. The calculator will then work out what your income tax will be as well as what the effective tax rate will be for your particular income level.

How did this come about?

The other day I was trying to figure out whether someone would pay more taxes living in New Zealand or the Cook Islands earning $80k NZD per year in 2021. So I jumped on Google and searched for a simple income tax calculator.

The New Zealand Income Tax Calculator

For New Zealand there were a bunch of different options. So after trying out a couple of them I settled on the income tax calculator available at https://www.paye.net.nz/calculator/. The website provides a fairly good calculator that did exactly what I needed.

Cook Islands Income Tax Calculator

For the Cook Islands there weren’t that many options. However I was able to find a pretty good tax calculator at https://www.icalculator.info/cook-islands/salary-calculator/annual.html. It took a few minutes to figure out how to work the interface but once I figured it out it was fairly straightforward.

Where would you pay less tax?

So it looks like if you have an income of $80k NZD / year, you would pay less tax living in the Cook Islands then in New Zealand. You’d have $1202 NZD / year in tax savings.

Building my own Cook Islands Income Tax Calculator

This got me wondering about building my own online income tax calculator for the Cook Islands. I knew I didn’t want to have to code up the income tax calculator from scratch, so I decided to use formidable forms (a WordPress plug-in) to implement the calculator. Unfortunately, It wasn’t as straight forward as I thought it would. I had to take some time to figure out a formula that would work with the limitations of Formidable Forms. The table below shows the income tax brackets.

Cook Islands Tax Rates Tables 2021

Income_Tax_Rate	Tax_Rate	Description
Income under $14,600	0%	Nil
Income from $14,601 – $30,000	17%	17c for each $1 over $14,600
Income from $30,001 – $80,000	27%	*$2,618 plus 27c for each $1 over $30,00
Income from $80,001 plus	30%	*$16,118 plus 30c for each $1 over $80,000

I’m terrible at math’s but after a couple of hours of tinkering I was able to cobble something together despite the limitations of Formidable Forms when it comes to building tax calculators. The formula was:

diff = max_income - min_income
diff_tax = diff * tax_rate
(((income - min_tax_rate) * diff_tax) / diff) + (prev_diff + prev_diff_tax)

Where

• max_income = the maximum income at a particular income bracket
• min_income = the minimum income at a particular income bracket
• diff = the difference between the maximum and minimum for a particular income bracket
• diff_tax = the maximum amount that can be taxed at that particular bracket
• tax_rate = what the tax rate is at a particular income bracket
• prev_diff = the previous tax brackets difference between the maximum and minimum for a particular income bracket
• prev_diff_tax = the previous tax brackets maximum amount that can be taxed at that particular bracket