Investment Boost was announced in Budget 2025 and the headline is easy to repeat: 20% of the cost of an eligible new asset, deducted immediately, with the rest depreciated as normal. Clients understood it within a week of the announcement, and most of them have been asking about it since.
The rate is not the part that goes wrong. The part that goes wrong is the date.
What Investment Boost actually does
For an eligible new asset, you deduct 20% of its cost in the first year. The remaining 80% becomes the asset’s depreciable value and runs off at the normal IRD rate over the rest of its life.
It is worth being precise about what that means, because clients often hear it as free money. It is not an increase in the deduction, it is an acceleration of it. Over the life of the asset the total claimed is the same. What changes is when it lands: a much larger deduction in year one, slightly smaller ones thereafter. For a client weighing up a purchase, that timing difference is the whole conversation, and it only holds up if the numbers underneath it are right.
The date that decides it
Investment Boost applies from 22 May 2025. The date it tests is the date the asset was first used, not the date it was acquired.
That distinction is not a technicality. Consider two clients who each ordered a machine in April 2025:
- The first took delivery in April and had it running that month. The asset was first used before 22 May 2025. No Investment Boost.
- The second had a longer lead time, took delivery in June and commissioned it then. Same order date, same invoice date, same supplier. Investment Boost applies.
Nothing on the invoice tells you which of these you are looking at.
Almost every other rule a New Zealand register deals with keys off the acquisition date. This one does not, and a register built around acquisition dates has nowhere to put the answer.
Why this breaks a spreadsheet register
Most depreciation spreadsheets have one date column. It gets labelled “purchase date” or “date acquired”, it is populated from the invoice, and every formula in the sheet hangs off it. There is no column for the date the asset was first put to work, because until May 2025 nothing needed one.
So the eligibility test gets made once, by whoever is preparing the return, from memory or from a conversation with the client. It is not recorded anywhere. Next year, nobody can explain why one machine got the boost and a near-identical one did not, and if the return is ever reviewed, the reasoning has to be reconstructed from scratch.
The failure mode here is familiar. It is the same one that produces assets still depreciating years after they were sold, and write-off thresholds applied from the wrong year. A judgement gets made correctly, is never written down, and quietly stops being defensible.
It applies to one book, not both
Investment Boost is a tax concession, so it belongs in the tax book. The accounting book should carry on depreciating the asset over its useful life on its full cost, because nothing about the asset’s economic life changed when the Minister of Finance stood up.
From year one, the two books diverge. That variance is real, it needs to be explained to whoever is reading the financial statements, and it compounds over the life of the asset. Where the register is one spreadsheet doing double duty as both books, this is where the two views quietly become one view, and the balance sheet ends up carrying the tax answer.
There is a second-order effect worth flagging too. For a GST-registered entity, the 20% is calculated on the cost after the GST credit, not the invoice total. Get the order of operations wrong and every subsequent year of depreciation on that asset is wrong with it.
What good looks like
None of this is difficult. It is just bookkeeping that has to be done deliberately rather than remembered.
A register that handles Investment Boost properly records the first-used date as a first-class field on the asset, separate from the acquisition date. It applies the 20% only to the books that follow tax rules. It applies it on the correct GST basis. And it keeps the working, so that in three years someone can see which date drove the decision without having to ask anyone.
The test is not whether you can get Investment Boost right this year. It is whether the register can still explain itself after the person who set it up has moved on.
That question is worth asking of any concession with a date gate on it, and New Zealand registers have several. The low-value write-off threshold has been $200, $500, $5,000 and $1,000 at different times, and the right one is the one that applied on the purchase date, not the one that applies today. The IRD prescribed rates have changed over the years as well. Each of these is easy to get right once and hard to keep right by hand.
The system underneath
In Dwindle, the first-used date sits on the asset, and Investment Boost is applied automatically to assets flagged as eligible where that date falls on or after 22 May 2025.
The remaining 80% then depreciates at the IRD prescribed rate for the asset’s class — a separate question from the boost, and one that turns on the acquisition date rather than the first-used date. Two rules, two different dates, and a register that handles New Zealand properly needs to hold both. The tax book takes the boost, the accounting book does not, and the variance between them is calculated rather than hunted.
Dwindle is depreciation software built on Australian and New Zealand tax concepts, with both the tax view and the accounting view in one place. Australian and New Zealand entities sit in the same group, each on its own rules and income year.
Eligibility for Investment Boost on any particular asset is a question for your tax advisor. Making sure the register can still justify the answer next year is a question about your systems.