Invoice Calculator NZ
This invoice calculator turns the hours on your timesheet into the numbers that go on a New Zealand invoice, and then into the amount that actually lands in your bank account. Those are rarely the same figure. A contractor billing $120 an hour for a 38.5 hour week does not receive $4,620: GST may be added on top, expenses may be passed on, and if the work is a schedular payment the client deducts withholding tax before paying. Inland Revenue's rule is that the tax comes off the GST-exclusive amount, so GST always reaches you in full while the tax is taken from everything else. You enter your hours at your main rate, any hours at a second rate such as after-hours or a senior rate, the expenses you are on-charging, whether you are GST registered and the withholding rate on your IR330C. The calculator gives you the invoice subtotal, the GST, the invoice total, the tax your client will deduct and the payment to expect, so you can check a remittance the day it arrives. It is built for sole trader contractors, fractional professionals and freelancers who bill by the hour, and for anyone checking a contractor's invoice. Rates and thresholds are those in force for the 2026/27 tax year.
From the same team as Calculate.co.nz
Your Timesheets at jobtracker.co.nz logs your hours on a week grid or a timer that keeps counting when your phone locks, free on every plan. Career and Timesheets turns those hours into projects and rates, fixed fees and retainers, numbered invoices with GST only when you are registered, expenses and mileage, and the tax to set aside, from $4.99 a month billed yearly.
Log your hours freeWithholding tax applies only to schedular payments, such as most labour-only contracts. If your client does not deduct it, enter 0.
How it works
The subtotal is your hours at each rate plus the expenses you are passing on, all excluding GST. If you are registered, GST is 15% of that subtotal, and the invoice total is the two added together. Withholding tax is your IR330C rate applied to the GST-exclusive subtotal, never to the GST. The payment you receive is the invoice total less that tax. The tax your client deducts is not lost: it is a credit against your income tax when you file your return, which is why a contractor whose rate is set too high gets a refund and one whose rate is too low gets a bill.
Worked example
A GST-registered contractor works 38.5 hours at $120 an hour, which is $4,620, and on-charges $85 of expenses, for a subtotal of $4,705.00. GST at 15% adds $705.75, so the invoice total is $5,410.75. The client deducts 20% withholding tax from the $4,705.00 GST-exclusive amount, which is $941.00, and pays $4,469.75. The full $705.75 of GST arrives with it, ready for the contractor's next GST return.
| Line | Amount |
|---|---|
| 38.5 hours at $120 | $4,620.00 |
| Expenses on-charged | $85.00 |
| Subtotal excluding GST | $4,705.00 |
| GST at 15% | $705.75 |
| Invoice total | $5,410.75 |
| Less withholding tax at 20% of $4,705.00 | $941.00 |
| Paid to you | $4,469.75 |
Related calculators
- Schedular Payments Calculator: the standard withholding rate for each activity.
- Tax Reserve Per Invoice Calculator: what to set aside from each invoice when no tax is deducted.
- Invoice Due Date Calculator: when the invoice falls due under common payment terms.
- Timesheet Rounding Calculator: how rounding each entry changes the hours you bill.