Business GST Calculator NZ 2026

This calculator works out GST payable or refundable for a New Zealand GST return, using the same three-part structure as the IRD GST101 return: sales and income, purchases and expenses, and the net GST summary for the period. In the sales and income section you enter your total sales and income, any zero-rated supplies (such as exports), and total debit adjustments; the calculator subtracts zero-rated supplies to find your net GST sales and income, then extracts the GST component at 15% to show total GST collected, adjusts for debit adjustments, and gives your total GST on sales and income. In the purchases and expenses section you enter total purchases and expenses and any credit adjustments; the calculator works out the GST included in your spending to show net GST paid and your total GST paid for purchases and expenses. The final summary subtracts GST paid from GST collected to show the amount you owe IRD, or the refund due, for the period. With the default figures of $10,000 in sales and $5,000 in purchases, the calculator returns $652.17 to pay. Use it each filing period to check your own return, or to estimate GST before you file, but always confirm the final figures in myIR before submitting, since this tool is a guide and not a substitute for professional advice or IRD's own systems.

In New Zealand, businesses registered for Goods and Services Tax (GST) are required to file periodic GST returns to the Inland Revenue Department (IRD). Accurate calculation and reporting of GST are crucial to ensure compliance with tax laws and avoid penalties. This guide will walk you through the IRD method for calculating business GST in New Zealand, covering the following fields: Sales and Income, Total Sales and Income, Zero-rated Supplies, Net GST Sales and Income, Total GST Collected on Sales and Income, Total Debit Adjustments, Total Purchases and Expenses, Net GST Paid, and Total Credit Adjustments.

Total Sales and Income
Sales and income refer to the total revenue generated by a business during a specific GST filing period. This includes all taxable supplies, such as goods sold or services rendered, as well as any other sources of income. To calculate your sales and income, simply add up all the revenue from your business transactions within the given period. Total sales and income is the aggregate of all the sales and income generated by the business, including GST. To obtain this figure, add the GST component to your sales and income figure.

Zero-rated Supplies
Zero-rated supplies are goods or services that are subject to GST but taxed at a 0% rate. These typically include exports and certain financial services. It's important to identify and record zero-rated supplies separately, as they need to be reported in your GST return but will not contribute to your GST liability.

Net GST Sales and Income
To calculate net GST sales and income, subtract the value of zero-rated supplies from your total sales and income. This figure represents the total sales and income that are subject to GST at the standard rate of 15%.

Total Debit Adjustments
Debit adjustments refer to any additional GST amounts you need to pay due to errors, adjustments, or changes in your business transactions. Examples of debit adjustments include bad debt write-offs, undercharged GST, or adjustments for assets used for both business and private purposes. Add up all the debit adjustments for the period and include this amount in your GST return.

Total Purchases and Expenses
Total purchases and expenses include all the costs incurred by your business during the GST filing period. This comprises the cost of goods sold, overhead expenses, and any other costs associated with running your business. Be sure to include the GST component when calculating your total purchases and expenses.

Net GST Paid
To calculate net GST paid, subtract the GST component included in zero-rated purchases (if any) from your total purchases and expenses. This will give you the amount of GST you have paid to your suppliers during the filing period.

Total Credit Adjustments
Credit adjustments refer to any reductions in the GST you have paid on your purchases and expenses. These adjustments may arise from overpaid GST, adjustments to input tax credits, or changes in the use of assets. Add up all the credit adjustments for the period and include this amount in your GST return.

Total GST Summary for Period
Net GST Payable/Refundable = (Total GST collected on sales and income - Total GST paid for purchases and expenses)