NZ Tax Code SB

SB is a flat-rate secondary code: instead of stepping up through NZ's progressive brackets from $0 the way a main job does, an employer using SB takes a single 10.5% off every dollar it pays you, with no tax-free amount and no threshold. That 10.5% is set to match the bottom tax bracket, on the basis that your secondary earnings sit on top of income already taxed through your main job — which is why a second job needs its own code rather than being taxed from zero all over again.

You work out which secondary code applies by adding up your expected annual PAYE income from every job — salary, wages, NZ Super, schedular payments, over the 1 April to 31 March year — using the secondary-income flowchart on page 3 of the IR330 Tax Code Declaration. SB is only correct when that combined total comes to $15,600 or less, which in practice means very light part-time or casual work across all your jobs put together. If your hours or pay change during the year and push the combined total higher, the code that fits also changes, and IRD expects a new IR330 once it does.

ACC earner's levy is charged on top of the 10.5%, at 1.75% on liable earnings up to $156,641 for 2026-27. Because SB sits at the bottom of the secondary-code ladder, the more common slip is staying on a higher code (usually S) after your combined income drops — that overtaxes the secondary job rather than undertaxing it. Either way IRD squares it up at the May–June auto-assessment (or an IR3 if one is required), billing a shortfall or refunding an overpayment. To correct the code going forward, hand the employer paying that income a new IR330 — they are required to apply it once you do.