Home Office Expenses Calculator Spreadsheet | GST & Income Tax Deductions
This resource presents a comprehensive home office deduction template designed for small business owners and sole traders in New Zealand, Australia, and the United Kingdom. The spreadsheet demystifies the typically complex process of calculating year-end tax deductions, traditionally handled by professional accountants.
Key benefits
Maximise income tax deductions
The calculator helps unlock significant tax savings by accurately computing deductions based on the percentage of your home used for business and your total operating expenses. This precision can substantially reduce your overall tax liability.
Claim GST/VAT credits with ease
For GST-registered individuals, the tool simplifies identifying and claiming eligible GST credits, which effectively lowers the net cost of your home office expenses.
How to use the calculator
Step 1: Download or make a copy
Begin by downloading or copying the spreadsheet to personalise it with your specific financial data.
Step 2: Populate with your expenses
Enter your expense information into the template. Include all relevant home costs:
- Rent or mortgage interest
- Electricity and gas
- Internet and phone
- Insurance and rates
- Cleaning and maintenance
Step 3: Enter your business use percentage
Calculate the percentage of your home used for business (typically floor area of office ÷ total floor area of home) and enter this figure. The spreadsheet applies it automatically across all expenses.
Step 4: Use the summary sheet
The Summary Sheet generates your potential tax deductions and GST credits automatically. Examine this summary for accuracy before proceeding.
Next steps
- Consult your accountant — Share your completed spreadsheet with an accounting professional for strategic financial insights and to ensure you're claiming correctly
- Sync with accounting software — Integrate summary data into your existing accounting application (e.g. Xero)
- DIY tax filing — Use the detailed figures to complete your IR3B tax form (NZ) while maintaining supporting documentation for at least 7 years
Automate this process with Prosaic
Rather than updating a spreadsheet manually each year, Prosaic automatically reads your bank transactions and identifies home office expenses — providing your accountant with a live, accurate view of claimable expenses throughout the year. Learn more about Prosaic's AI-powered home office expense tracking.