If you own a holiday home, bach, boat, or aircraft that you both rent out and use privately, the GST you can claim depends on the apportionment between income-earning and private use. This calculator implements the days-used formula (income-earning days ÷ total used days), tests the $50k boat/aircraft threshold, and applies the $4k opt-out rule. It also shows the simplified general apportionment treatment that applies from 1 April 2024 alongside the old section 20G method.
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.
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.
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.
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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