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The Treasury's CBAx Tool

CBAx is a spreadsheet model by the Treasury that contains a common database to help agencies monetise impacts and do return on investment

The Treasury first released CBAx, a cost benefit analysis (CBA) tool, in October 2015. The CBAx version for Budget 2018 was released in September 2017.

The Treasury provides a CBA tool called CBAx

The Treasury encourages important public sector decisions to be informed by cost benefit analysis.

To help compare different options in New Zealand, the Treasury has developed a CBA tool called CBAx. CBAx is a spreadsheet model that contains a common database to help agencies monetise impacts and do return on investment analysis. 

The CBAx tool helps agencies:

  • to monetise and discount impacts, ie, CBA steps 4 and 5
  • to take a long-term and broad view of costs and benefits
  • to rigorously assess these by monetising impacts, where possible, and
  • to be transparent about the assumptions and evidence base.

Many factors are considered in the decision-making process. Initiatives are not evaluated on CBAx results alone.  CBAx results together with unmonetised impacts, evidence base and assumptions inform value for money (VFM) advice. VFM is considered along-side the wider case and factors eg, strategic alignment with Government priorities, fiscal constraints and implementation risks.

In the budget context, the CBAx analysis is used primarily by the Treasury vote team in developing VFM advice. 

The CBAx spreadsheet tool has been designed specifically with social sector agencies in mind, but can be used to help calculate return on investment for many initiatives. The CBAx tool helps people to do in-house CBAs. See the Treasury's guidance on using CBAx in:

Further guidance on undertaking a CBA in

The Treasury welcomes suggestions on the CBAx tool and would like to learn from practical experiences of applying CBAx. Over time, the Treasury will improve and update the tool. We welcome feedback and insights from people within and outside the public sector. Please contact with comments and suggestions.

CBAx is a spreadsheet model with an impact values database

The CBAx tool is a spreadsheet model:

which provides:

  • a common model for organisations to use when analysing costs and benefits of initiatives
  • a common basis for assumptions when quantifying and monetising the impacts of different proposals
  • a common database to help organisations estimate broader societal impacts, making analysis quicker and providing consistent assumptions.

We recognise that there will always be limitations to a tool like CBAx. To be able to use the CBAx tool, organisations need to quantify impacts and success rates, for example the number of people expected to gain employment, based on the best available data and evidence about the relevant impacts of an initiative. There will sometimes be gaps in the evidence for how effective an initiative might be, for example when trying something new.

The advantage of the CBAx tool is that it makes assumptions explicit, and values different types of costs and benefits in a consistent way. This provides the basis for a more informed discussion between different options. Discussions should consider all impacts including unmonetised impacts, as well as those impacts able to be monetised using the CBAx tool.

CBAx impact values database

CBAx contains a database of New Zealand specific publicly available data that organisations can use to value impacts. An impact value provides a numerical value in relation to one or more impacts of an initiative. In some situations a value may be a cost, in others it could be a benefit or a saving. Examples include the costs of an emergency department visit, the cost of the Jobseeker Support benefit and increased income for individuals. The values are adjusted to reflect a common time period. The CBAx tool allows agencies to add their own values for impacts into the model.

The Treasury invites people to suggest data and information for inclusion in the CBAx database. This may be information that is available and that can be shared, or it may be a request for values that people would find helpful to have included in CBAx. The Treasury anticipates refreshing CBAx on an annual basis.

The Treasury purchased a licence for the Australian Social Value Bank in 2017. This significantly extends the wellbeing values available to use in CBAx. If a New Zealand government agency would like to purchase a sub-licence and use New Zealand applicable values in CBAx modelling, then please contact

In 2016, the Treasury hosted Daniel Fujiwara, who provided an introduction to the Australian Social Value Bank methodology in the Treasury Guest Lecture on Social Impact Values. 

User-driven improvements to the CBAx tool and its use

As agencies build their CBA capability, the CBAx tool remains familiar and has no structural changes. The improvements are in response to user feedback. Changes are mainly to the templates, the guidance and the use of CBAx, including:

  • Fit for purpose application, through more targeted budget requirements, clarification of grounds for exemptions, and increased use and visibility. 
  • Availability of Australian Social Value Bank values. Government agencies can purchase a sub-licence through the Treasury and use wellbeing impact values in CBAx.
  • Model improvements that do not affect the way in which you use CBAx. The discount rates remain unchanged, and are consistent with the rates in October 2016.

The CBAx Tool User Guidance has been significantly updated to respond to feedback from the review and include tips from Budget experiences. The budget initiative and impact summary templates  were updated in September 2017. Applied examples of CBAx are available as part of the Budget 2016 and Budget 2017 Information Release.


Last updated: 
Wednesday, 27 June 2018