This calculator works out how much GST input tax you can claim on a holiday home, bach, boat or aircraft that you both rent out for income and use privately during the year. Because a straight 100% GST claim is not allowed on a mixed-use asset, you can only claim the income-earning share, alongside separate income tax rules running in parallel. You enter the asset type, its GST-inclusive cost (or market value), the days it earned income at market rates, the days it was used privately, the days it sat unused, your gross rental income, your mixed expenses covering both uses, and any expenses relating only to income-earning use. The calculator returns the total days used, your income-earning use percentage, the GST hidden inside your mixed expenses, the apportioned claim on those expenses, the full claim on pure income-earning expenses, and your total GST input tax claim. It also flags whether your boat or aircraft meets the $50,000 mixed-use threshold, whether the asset passes the 62-day unused test, and whether your rental income is low enough to opt out of the mixed-use rules altogether. Use it to sanity-check a GST return or to weigh up whether opting out saves more in compliance hassle than it costs in forgone claims. This is a planning tool only, so confirm your figures and eligibility with an accountant or IRD before filing.
Updated April 2026
Reflects the 1 April 2024 simplification: section 20G method is no longer mandatory but remains an acceptable fair and reasonable method.
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Asset details
$
Annual usage (days)
days
days
Includes use by associated persons (family, friends paying mates' rates) and any use by anyone paying less than 80% of market rate.
days
Days the asset was sitting empty. Excluded from the apportionment formula. Total of all three should equal 365.
Income earned
$
Mixed expenses (relate to BOTH uses)
$
Rates, insurance, building maintenance, depreciation, utilities. Excludes purely income-earning expenses (advertising, cleaning fees) and purely private expenses.
$
Advertising, booking platform fees, cleaning between guests, linen hire. These give a full GST credit regardless of usage split.
Mixed-Use Asset GST Result
Total used days (income + private)
0
Income-earning use percentage
0%
Mixed expenses (GST inclusive)
$0
GST in mixed expenses (3/23)
$0
Apportioned mixed expense GST claim
$0
Pure income-only expenses GST claim (100%)
$0
Total GST input tax claim
$0
The mixed-use asset rules in 2026
From 1 April 2024, IRD simplified the GST treatment of mixed-use assets. The special section 20G calculation is no longer mandatory. Owners can use the general GST apportionment rules instead, OR continue with the old section 20G formula as a "fair and reasonable" method. Both produce similar results in most cases. The income tax mixed-use asset rules still apply separately.
The apportionment formula
Income-earning use percentage = income-earning days ÷ (income-earning days + private days). Days the asset is unused (vacant) are excluded entirely - they neither help nor hurt your GST claim.
This percentage is applied to mixed expenses (rates, insurance, building maintenance, depreciation - things that relate to both income and private use). Pure income-only expenses (advertising, cleaning between guests) are 100% claimable. Pure private expenses are 0% claimable.
The $50,000 threshold for boats and aircraft
Boats and aircraft only fall under the mixed-use rules if they cost $50,000 or more. A $30,000 jet ski rented occasionally falls under standard apportionment rules instead. Holiday homes have no minimum threshold.
Opt-out for low income
If gross income from the income-earning use of the asset is less than $4,000 in the tax year, you can opt out of the mixed-use asset rules entirely. No income to declare, no expenses to claim, no GST adjustments. Useful for occasional Airbnb users or someone who chartered the boat once.
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