First-Year Provisional Tax Safe-Harbour Calculator
First year of self-employment? You don't pay provisional instalments during the year — the full RIT falls due as terminal tax. This calculator checks whether you're inside IRD's $60,000 safe harbour and previews next year's instalment schedule.
Self-employed profit after expenses, plus any other taxable income.
If you also had a PAYE day job, RWT on interest, or imputation credits, enter the total withheld.
Income tax paid on or before your balance date, or through tax pooling. Used for the early-payment discount below.
How first-year provisional tax works
The standard provisional method calculates instalments as 105% of last year's RIT, split across three dates. In your first year of self-employment there's no prior-year RIT to multiply, so no instalments are required — but the full first-year tax balance is owed in one hit on terminal tax day.
IRD's $60,000 safe harbour (Tax Administration Act 1994 s 120KE) protects first-year filers from UOMI as long as RIT stays under the threshold, you have not estimated or used AIM or a GST ratio, and the balance is paid on time. From $60k, UOMI can start before your terminal tax date. If you stopped employment and started this business during the year, and your residual income tax was $5,000 or less in each of the four previous tax years, IRD treats the tax as due in instalments on 28 August, 15 January and 7 May (the dates at least 30 days after you started), and interest runs from the day after each. Otherwise interest runs from the day after the final instalment date (7 May), not from the tax year-end.
From year 2 onwards, you enter the standard provisional regime with three instalments (28 August, 15 January, 7 May for a 31-March balance date; two, on 28 October and 7 May, if you pay GST 6-monthly). The base for the calculation is your year-1 RIT × 105%.
UOMI walkthrough — what late payment actually costs
Use-of-Money Interest (UOMI) applies from the instalment dates once your RIT reaches the $60,000 safe-harbour threshold, if you stopped employment and started the business during the year. The rate is 8.97% p.a. simple (IRD's underpayment rate effective 16 January 2026), calculated daily, and applied from the date each instalment should have been paid until the date it actually is. Every published rate and effective date is on the IRD UOMI rates page.
Worked example — year-1 RIT $90,000, after leaving employment to start the business before the first date
- $90k RIT is outside the $60k safe harbour → UOMI runs on each instalment amount below, not only the part above $60k
- Standard schedule would have been: P1 (28 Aug) $30k, P2 (15 Jan) $30k, P3 (7 May) $30k
- You pay all $90k at terminal tax (7 Feb following year-end, i.e. ~22 months after P1)
- P1 segment: $30k × 8.97% × (530 days ÷ 365) ≈ $3,907 UOMI
- P2 segment: $30k × 8.97% × (388 days ÷ 365) ≈ $2,861 UOMI
- P3 segment: $30k × 8.97% × (276 days ÷ 365) ≈ $2,035 UOMI
- Total UOMI: ~$8,803 on top of the $90k tax
The numbers swing dramatically based on how late you pay. Paying P1 only 30 days late costs ~$221 of UOMI; paying it 530 days late (i.e. paying everything at terminal tax) costs ~$3,907. If you expect RIT above $60k, voluntary year-1 instalments are nearly always cheaper than the UOMI bill. The estimation method (below) lets you forecast and pay voluntary instalments. If you are already past a due date, the late filing penalty calculator adds the 1% and 4% late payment penalties to the interest.
RIT calculation walkthrough
Residual income tax (RIT) = income tax owed minus tax already withheld through PAYE, RWT (Resident Withholding Tax on bank interest), and imputation credits. RIT determines both provisional-tax enrolment and safe-harbour eligibility.
Worked example — mixed PAYE + self-employed
- PAYE salary: $80,000 (PAYE withheld: ~$15,500)
- Self-employed business profit: $50,000 (no tax withheld)
- Bank interest: $1,200 with $360 RWT withheld at 30%
- Total taxable income: $131,200
- Income tax (progressive 10.5/17.5/30/33/39%): ~$34,946
- Less tax already withheld: $15,500 (PAYE) + $360 (RWT) = $15,860
- RIT = $34,946 − $15,860 = $19,086
- Above $5,000 → provisional tax applies in year 2
- Below $60,000 → year-1 safe harbour applies (no estimate, AIM or GST ratio); no UOMI if terminal tax paid on time
For a pure self-employed person with no PAYE day job, RIT roughly equals the income tax calculation on business profit (after deducting allowable expenses). For a mixed earner, RIT only captures the un-withheld portion.
Voluntary instalments — when they pay off
If you forecast RIT above $60,000 in year 1, voluntary instalments via the estimation method nearly always cost less than UOMI. The trade-off is cashflow vs interest.
Pay-at-terminal strategy
- Pros: maximum cashflow flexibility through year 1
- Cons: large lump-sum due on 7 Feb (or 7 Apr on agent's list)
- UOMI cost if RIT reaches $60k: ~8.97% on the amount unpaid at each date it runs from, simple daily
- Best when: RIT genuinely under $60k OR business is cash-strapped
Estimation method (voluntary)
- Forecast year-1 RIT, divide by 3, pay at 28 Aug / 15 Jan / 7 May
- Pros: no UOMI as long as your estimate ≥ actual
- Cons: requires cash discipline; under-estimate triggers UOMI from each missed date
- Best when: RIT expected above $60k and cashflow allows quarterly hits
Safety margin for estimation: err on the high side. If you under-estimate by 30%, UOMI applies on the shortfall. Most CPAs recommend estimating at 110% of your honest forecast — paying a bit too much early is recovered at terminal tax as a refund with no UOMI penalty. Under-estimating saves cashflow short-term but exposes you to the same UOMI as pay-at-terminal.
Year 2 — standard uplift and the cashflow cliff
Year 2 brings the cashflow cliff that catches first-year self-employed people off-guard. You owe both: (1) year-1 terminal tax on 7 February, AND (2) three year-2 provisional instalments based on year-1 RIT × 105%.
Year-2 cashflow example — year-1 RIT $25,000
- Year 2, 28 Aug 2026: provisional P1 = $25k × 1.05 × ⅓ = $8,750
- Year 2, 9 Feb 2027 (7 Feb is a Sunday, 8 Feb is Waitangi Day observed): year-1 terminal tax = remaining $25k year-1 balance owing
- Year 2, 15 Jan 2027: provisional P2 = $8,750
- Year 2, 7 May 2027: provisional P3 = $8,750
- Plus: year-2 terminal tax due 8 Feb 2028 (Waitangi Day falls on Sunday 6 Feb, so Monday 7 Feb is the public holiday; year-2 RIT minus the three instalments)
- 12-month cash outflow: ~$51,250 (your year-1 tax + year-2 instalments)
Plan for this in year 1: open a high-interest savings account and set aside ~35-40% of net business profit each month. By year-2 P1 (28 Aug) you'll have ~17 months of savings to cover year-1 terminal tax + year-2 P1 + part of P2 — enough buffer to ride out the cashflow concentration. Reverting to under-saving puts you in the UOMI trap from year 2 onwards.
AIM — alternative for variable-income businesses
The Accounting Income Method (AIM) is a third provisional tax method, designed for small businesses with seasonal or variable income. AIM uses your accounting software (Xero, MYOB, Reckon) to calculate instalments based on actual current-period results, paid every two months alongside GST.
- Eligible: annual gross income of $5 million or less in the previous tax year
- Pay GST and provisional tax in the same return, every 2 months
- No UOMI risk — instalments match actual income, not estimates
- Available only if you use AIM-capable accounting software
- You can start AIM part-way through the year: if you began the year on the standard or GST ratio method and have met all your provisional tax obligations so far, you can change to AIM for the remaining instalments (Income Tax Act 2007 s RC 5(5B)(a)(ii))
AIM is most useful for businesses with seasonal swings (e.g. summer hospitality, winter tourism, term-time tutoring). For steady-revenue businesses, the admin overhead of bi-monthly filing usually outweighs the UOMI protection. Talk to your accountant or tax agent before electing AIM. You choose AIM for a particular tax year (Income Tax Act 2007 s RC 5(5B)(a)), and if you stop meeting the AIM conditions part-way through the year you are treated as using the estimation method for the whole of that year (s RC 5(5C)).
Frequently asked questions
Do I have to pay provisional tax in my first year of self-employment?
No, not mandatorily. Standard provisional uses 105% of prior-year RIT — and your prior year RIT is zero. The full RIT is owed as terminal tax. Optional voluntary instalments are available via the estimation method if you want to spread the cash flow or avoid UOMI when RIT exceeds the $60k safe harbour.
What counts as RIT?
Residual income tax = income tax owed for the year minus PAYE / RWT / imputation credits already withheld. For pure self-employed with no PAYE day-job, RIT roughly equals the income tax on your business profit. For mixed earners, RIT only captures the un-withheld portion (typically self-employed + investment income).
What happens if I'm above the $60k safe-harbour threshold?
You don't lose the right to pay at terminal tax time — but UOMI runs up to the date you eventually pay. If you stopped employment and started this business during the year, and your residual income tax was $5,000 or less in each of the four previous tax years, IRD treats the tax as due in instalments on 28 August, 15 January and 7 May (the dates at least 30 days after you started), and interest runs from the day after each. Otherwise interest runs from the day after the final instalment date (7 May), not from the tax year-end. The rate is currently 8.97% p.a. simple daily (IRD's underpayment rate effective 16 January 2026), so the longer the gap, the worse the bill. If the instalment dates apply, a $90k RIT paid entirely at terminal tax costs ~$8,803 of UOMI on top of the tax owed.
Can I use the estimation method instead?
Yes. The estimation method lets you forecast your own current-year RIT and pay one-third at each provisional date. Used well, it caps UOMI exposure. Under-estimate and UOMI applies from each missed instalment — so estimate generously (110% of your honest forecast is a common rule). Estimating aggressively to minimise cashflow puts you in the same UOMI trap as pay-at-terminal.
What changes in year 2?
You move onto standard uplift: instalments are 105% of year-1 RIT (110% of the year before's RIT only while year 1's return is not yet due under an extension of time and not yet filed), split equally across 28 Aug, 15 Jan, and 7 May. The terminal tax wash-up runs the following 7 Feb. Year 2 has the cashflow cliff: you owe year-1 terminal tax AND three year-2 instalments within the same 12 months. Plan in year 1 by setting aside 35-40% of net profit each month.
Is AIM (Accounting Income Method) a good fit for me?
AIM works best for variable-income or seasonal businesses whose annual gross income for the previous tax year was $5 million or less, and that already use AIM-capable accounting software (Xero, MYOB Essentials, Reckon). Instalments are calculated bi-monthly from actuals, so there's no UOMI risk. The trade-off is more frequent filing (every 2 months) and reliance on accounting software being up-to-date. For steady-revenue businesses, standard or estimation methods are simpler.
What if my income drops significantly in year 2 vs year 1?
Switch to the estimation method early in year 2. Forecast your year-2 RIT honestly and pay one-third at each instalment. IRD cannot charge UOMI if your actual year-2 RIT is at or below your estimate. The risk is under-estimating; buffer 10-15% above your honest forecast. The standard uplift (105% of year 1) over-collects when income falls, so estimation is the right move when revenue is genuinely lower.
Can I pay provisional tax weekly or fortnightly to smooth cashflow?
Yes — voluntary payments outside the standard three dates are accepted via IRD myIR. Set up a savings transfer to IRD's tax pool or use tax-pooling services (e.g. Tax Management NZ, Tax Traders) to deposit weekly/fortnightly and have it credited to your provisional account. Tax pooling can also reduce UOMI for shortfalls — the pool 'sells' you back-dated tax credits that offset the missed instalment date, typically at a lower interest rate than IRD's UOMI rate.
Related calculators
Sources
Safe-harbour rules from IRD — Safe-harbour rules and IRD — Provisional tax. UOMI rate from IRD — Use of money interest.