A second job is not taxed twice. It is taxed as if the lower PAYE bands have already been used by your main job, so payroll applies a single flat rate instead of walking through the brackets again. That flat rate is your secondary tax code. Get the code right and the two payslips should roughly add up to what one job at the combined income would have withheld. Get it wrong and you either fund IRD an interest-free loan all year, or owe a bill after 31 March.
Why the second job cannot reuse the 10.5% band
Income tax in 2026-27 is progressive: the first $15,600 is taxed at 10.5%, then 17.5% up to $53,500, and so on. Those bands apply to your total taxable income, not to each employer separately. If both employers started at the bottom band, too little tax would come out. The secondary code is the practical fix: the second employer withholds at a rate that matches where your combined income sits.
Which code: SB, S, SH, ST or SA
Inland Revenue publishes the secondary codes against total expected income for the year. For 2026-27 the usual mapping is SB at 10.5% when combined income stays in the lower bands, S at 18%, SH at 30%, ST at 33%, and SA at 39% once you are in the top band. You choose the code from your total income — main job plus second job, plus anything else taxable — not from the second job alone. A weekend café role on top of an $90,000 salary is not an SB situation just because the café pays little.
The no-notification rate
If you do not give the second employer a tax code, they must withhold at the no-notification rate of 45%. That is deliberately high. It protects IRD; it does not mean you owe that rate as a final tax. You can get the difference back through an automatic square-up or a return, but your cashflow during the year will look worse than it needs to. Completing a tax code declaration is almost always the cheaper move.
ACC, KiwiSaver and student loan still apply per job
Secondary tax is only the income-tax line. Each employer will still deduct the ACC earners’ levy at 1.75% of liable earnings (until you hit the annual cap of $156,641 across the year), KiwiSaver if you contribute, and student loan at 12% of income over $24,128 if your code includes SL. Two jobs can therefore push you over the student-loan threshold even when neither job would have done it alone. The ACC cap is annual: once combined earnings pass it, further levy should stop, but payroll at job two cannot see job one, so you may overpay ACC during the year and square it up later.
How to use the calculator for two jobs
Run the main job as a primary income with your usual KiwiSaver and student-loan settings. Then switch the tool to a second job and enter the extra gross — the engine applies the flat secondary code that matches the combined income instead of the brackets. Add the two take-home figures. That total is the planning number; it is still an estimate, because mid-year hours, a third gig, or a tax-code change will move the square-up. For the legal codes and the IR330 form, Inland Revenue is the authority.