Why is the second year of self-employment more expensive than the first?

Because two tax years collide. In your first year nothing is withheld, so the whole bill falls due as terminal tax after you file. If that bill is large enough, you also enter the provisional tax regime for the second year, which means paying toward the second year's tax in instalments while the first year's bill is still being settled. Neither amount is wrong or unexpected on its own; the difficulty is that they arrive close together, and a first year budget that covered only the first year's tax will not cover both.

What is residual income tax?

It is your income tax for the year after deducting any tax credits, but before deducting tax already paid such as PAYE or provisional instalments. It matters because it is the figure Inland Revenue tests to decide whether you must pay provisional tax the following year. If your residual income tax for a year exceeds the threshold, you are a provisional taxpayer for the next one. The threshold is a fixed dollar amount that is set by legislation and should be checked against Inland Revenue's current guidance.

How is provisional tax calculated in the first year I have to pay it?

The standard method uses an uplift: your previous year's residual income tax plus 5 percent, paid in three instalments across the year. It is deliberately based on the year you have already finished, because that figure is known, and it means a growing business underpays and a shrinking one overpays. You can instead use the estimation method and pay based on what you expect to earn, but underestimating exposes you to use of money interest, so most people in a first provisional year stay with the uplift.

Can I avoid the double hit?

You cannot avoid owing the money, but you can avoid being surprised by it. The two practical options are to set aside a share of every payment from your first day of trading, which is what this calculator sizes, or to use a tax pooling provider to spread the timing at a cost. Voluntary early payments toward provisional tax are also possible. What does not work is treating your first year's low tax as the normal state of affairs, because it is the only year that will ever look like that.

Does this include GST?

No. GST is a separate obligation with its own filing frequency and due dates, and it is not income tax. If your turnover has passed the registration threshold you will be handling GST returns alongside everything here, and the money collected as GST was never yours to spend. Treat it as a third stream to reserve, not as part of the figures on this page.

First Year Self-Employed Tax Bill Calculator NZ 2026

Rates current for the 2026/27 tax year. Reviewed 5 August 2026.

Quick answer On $80,000 of first-year income with $12,000 of expenses, your terminal tax for year one is $13,810.50. Because that exceeds the provisional threshold, year two brings three instalments of $4,833.68 each. The first of those falls due alongside the year one bill, so the peak you need to fund is $18,644.18, not $13,810.50. Setting that aside over 12 months costs $1,553.68 a month.

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The first year of self-employment is the cheapest tax year you will ever have, and that is precisely what makes the second one difficult. Nobody withholds anything from what you invoice, so no tax is paid at all during year one and the entire liability arrives at once when the return is filed. If that liability is large enough to cross the residual income tax threshold, Inland Revenue also brings you into the provisional tax regime for year two, which means paying instalments toward the second year's tax on a schedule that begins before the first year's bill is even settled. Two years of tax therefore land within a few months of each other, and a business that budgeted only for the first year finds itself funding roughly one and a half years of tax out of one year of trading. Nothing has gone wrong when this happens. It is the designed behaviour of a system that has no way to withhold from self-employed income, and it catches people every year because the first year gives no warning of it. This calculator shows both amounts, when each is due, and what putting the money aside from today would cost per month.

Year one income Gross, before expenses

Year one deductible expenses Tax applies to profit

Residual income tax threshold Check Inland Revenue's current figure

Months you have to save Until the first payment is due

Year one terminal tax

$13,810.50

Due after you file

Peak you must fund
$18,644.18
Year one bill plus first instalment

Save per month

$1,553.68

over 12 months

Year one

Income$80,000.00

Less deductible expenses$12,000.00

Taxable profit$68,000.00

Income tax$12,620.50

ACC earner levy$1,190.00

Terminal tax owed$13,810.50

Residual income tax testAbove threshold, provisional applies

Year two provisional tax

MethodStandard uplift, previous year plus 5%

Uplifted residual income tax$14,501.03

Payable in3 instalments

Each instalment$4,833.68

Year two total, if income is unchanged$14,501.03

What falls due, and when

Dates follow a standard 31 March balance date with GST filed six-monthly or not at all. Your own dates depend on your balance date and GST cycle, so confirm them with Inland Revenue.

When	What	Amount	Running total

The rules this uses, and where they come from

Provisional tax applies if residual income tax exceeds$5,000

Standard option uplift, no extension of time to filePrevious year RIT plus 5%, always

Standard option uplift, with an extension of time5% or 10%, depending on when you file

Instalments, standard3 a year

Instalments, if GST registered on 6-monthly returns2 a year

Early payment discount, first year in businessAvailable on voluntary payments

Sources: Inland Revenue, Provisional tax and Provisional tax options, standard option. Read 5 August 2026.

This is an estimate, not tax advice. It covers income tax and the ACC earner levy on business profit, and models the standard option at the 5% uplift over three instalments, which is what applies to most people leaving a first year of business. The 10% uplift on the RIT from two years ago only arises if you have an extension of time to file and then file after a provisional date; without an extension of time it is your previous year's RIT plus 5% regardless of when you file. If you are GST registered on six-monthly returns you pay two instalments rather than three. It does not model GST itself, the ACC work levy, student loan repayments, Working for Families, or use of money interest. Confirm your position with Inland Revenue.

Worth knowing in your first year Because you are not yet a provisional taxpayer, voluntary payments made before the end of the income year can attract an early payment discount. You must get most of your income from the business, make the payment before the income year ends, apply on or before your return is due, and have had no provisional tax obligation in that year or the four before it. The discount rate is set each year. See Inland Revenue, Paying tax in your first year in business.

Why the uplift method uses last year's number

Provisional tax has to be paid before the year it relates to has finished, so it cannot be based on that year's actual result. The standard method solves this by using the year you have already completed and adding 5 percent. The consequence is that a business growing quickly underpays through the year and faces a further terminal bill, while one that is shrinking overpays and waits for a refund. Neither is a mistake in the calculation; it is the cost of paying tax on income that has not been earned yet.

The threshold is what triggers everything

Whether year two is difficult or ordinary comes down to a single test: whether your residual income tax for year one exceeded the threshold. Below it, nothing changes and you simply pay the bill. Above it, the instalment schedule begins. Because the threshold is a fixed dollar amount rather than a percentage, it is crossed at a fairly modest level of profit, and most people who go self-employed full-time cross it in their first year without realising the test exists.

Worked example

A contractor's first year brings in $80,000 with $12,000 of deductible expenses, so taxable profit is $68,000. Income tax on that is $12,620.50, and the ACC earner levy at 1.75% adds $1,190.00, giving terminal tax of $13,810.50. That is comfortably above the residual income tax threshold, so provisional tax applies for year two.

Year two's provisional tax uses the standard uplift: $13,810.50 plus 5 percent is $14,501.03, paid in three instalments of $4,833.68. The first instalment falls due at the same point in the calendar as the year one terminal tax, so the amount that must be found at once is $18,644.18. Across the full second year the total paid to Inland Revenue is the year one bill plus all three instalments, which is $28,311.54, against a first year in which nothing at all was paid.

How this is calculated

Taxable profit is year one income less deductible expenses. Income tax is calculated on that profit using the personal rates in force from 1 April 2025: 10.5% to $15,600, 17.5% to $53,500, 30% to $78,100, 33% to $180,000, and 39% above that. The ACC earner levy is 1.75% of profit, capped at maximum liable earnings of $156,641. Terminal tax is the sum of the two, and it is compared against the residual income tax threshold you enter to decide whether provisional tax applies. Provisional tax uses the standard uplift of terminal tax plus 5 percent, divided into three equal instalments. The peak figure is terminal tax plus one instalment, being the amount falling due at the same time.

Related NZ calculators

Provisional Tax Calculator for the instalments in detail
Provisional Tax Due Date Calculator for your own dates
Irregular Income Tax Smoothing Calculator for reserving as you go
AIM vs Standard Provisional Tax for the alternative method
Tax Pooling Benefit Calculator for spreading the timing
Self-Employed Tax - Getting Started Right (NZ)