GST Change of Use Adjustment Calculator NZ 2026

This calculator works out the GST wash-up adjustment required under sections 21 and 21G of the GST Act 1985 when an asset's actual business use ends up different from what you estimated at purchase. Enter the GST-inclusive purchase price (the input tax claimed pre-fills automatically), the percentage intended use you estimated at acquisition, the percentage actual use at the end of the adjustment period, and which adjustment period number you are in. It applies the formula input tax multiplied by the difference between actual and intended use, then checks this against the de minimis thresholds of a 10 percentage point deviation or a $1,000 difference. Your results show the total input tax, the intended and actual use percentages, the deviation in percentage points, whether the wash-up threshold has been met, the dollar adjustment amount, and the treatment required: claiming additional input tax, paying output tax, or no adjustment at all. A detail breakdown sets out the full working so you can see exactly how the figure was reached. Use it at the end of each income year to check whether a change of use adjustment applies to assets used partly for taxable purposes and partly for private use or exempt supplies. This is a planning guide; confirm the adjustment period count and final figures for your asset with your accountant or Inland Revenue before filing your GST return.

Updated  Implements sections 21 and 21G of the GST Act 1985 (general apportionment rules).
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Asset details

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$
For NZ-purchased assets with GST in the price, this is purchase price × 3 ÷ 23. Pre-fills automatically from the GST-inclusive price above.

Use percentages

%
The percentage you originally estimated would be used in your taxable activity (i.e. excluding private use, exempt supplies, and use to make exempt supplies).
%
The actual taxable use over the adjustment period (typically one income year).

Adjustment period number

Asset value determines how many periods you must track: assets ≤ $5k need no adjustment; ≤ $10k = 2 periods; ≤ $500k = 5 periods; over $500k = 10 periods.

How the change of use rules work

When you acquire an asset for use partly in your taxable activity and partly for non-taxable purposes (private use or making exempt supplies), GST input tax is claimed proportionally based on your estimate of intended business use. Sections 21 and 21G of the GST Act 1985 then require you to revisit that estimate at the end of each adjustment period and wash up any difference between estimated and actual use.

The de minimis thresholds

An adjustment is only required if either: the percentage actual use deviates by 10 percentage points or more from the percentage intended use, OR the dollar value of the adjustment would exceed $1,000. Below both thresholds, no wash-up is needed, which significantly reduces compliance work for small variations in use.

Number of adjustment periods

  • Assets up to $5,000 (GST exclusive): no adjustments required
  • $5,001 to $10,000: 2 annual adjustments
  • $10,001 to $500,000: 5 annual adjustments
  • Over $500,000 (typically land): 10 annual adjustments

Sources

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Frequently asked questions

What is a GST change of use adjustment in NZ?

A GST change of use adjustment is required when the actual business use of an asset differs from your original estimate at the time you claimed input tax. The GST Act treats changes in use as a self-supply: if business use increases above your original estimate you can claim more input tax, and if business use decreases below your estimate you must pay output tax to reverse the over-claimed credit.

When is a GST adjustment required?

A wash-up adjustment is only required when the percentage actual use at the end of an adjustment period deviates by 10 percentage points or more from the percentage intended use, OR when the dollar difference exceeds $1,000 even if the percentage change is smaller. Below both thresholds, no adjustment is needed and the original input tax claim stands. The annual adjustment period typically runs for the income year.

How is the GST adjustment formula calculated?

The formula is: Adjustment = Total input tax × (percentage actual use − percentage intended use). A positive result means you can claim additional input tax. A negative result means you must pay output tax to reverse the over-claimed amount. The adjustment is included in your GST return for the period in which the adjustment period ends.

How many adjustment periods do I need to track?

The number of adjustment periods depends on the asset value: assets up to $5,000 (GST exclusive) need no adjustment after year 1; assets up to $10,000 need 2 annual adjustments; up to $500,000 need 5 annual adjustments; and assets over $500,000 (such as land and buildings) need 10 annual adjustments. After the final adjustment period, no further wash-ups are required.