Verify or certify? Validate or assure? How to choose the right check for your GHG emissions

You’ve calculated your greenhouse gas (GHG) emissions - great work.
Now comes the next question: how do you show that your numbers are correct?

With more regulations requiring independent checks on GHG data in Australia and New Zealand, understanding the options has never been more important. Should you verify your data? Validate it? Get assurance? Or go for certification? The terms sound similar, but they serve different purposes.

This guide explains what each option means, when to use it, and how to decide what’s right for your organisation.

 
Why independent checks matter

Independent evaluation gives you confidence that your GHG data is robust, transparent, and compliant with the standards you report against. It helps you:

• identify errors and improve data quality
• reduce greenwashing risks
• meet regulatory and investor expectations
• communicate results credibly
• Independence matters too. A third-party reviewer brings objectivity and credibility - for your board, investors, customers, and regulators.

 
Choosing the right GHG evaluation approach

Verification vs validation

Verification checks whether your past or current GHG data is correct and meets reporting standards. It looks backwards and confirms that your reported emissions are free from material errors.

Validation looks forward. It checks whether your future claims, assumptions, or reduction targets are reasonable and based on sound methods.

Both follow ISO 14064-3:2019, the international standard for verification and validation.

Ask yourself:

Are you reporting or disclosing your emissions publicly?

• If regulations or stakeholders require checks you need verification (with limited or reasonable assurance).
• If not → External review may be enough.

Are you setting new or updated emissions reduction targets?

• Validation helps test your assumptions and pathways.

What about an external review?

An external review gives you independent feedback without the full formality of verification. It’s a technical sense check of your data, methods, or reporting approach.

It won’t give you an assurance statement, but it helps you catch potential issues early - before you publish or commission verification.

Ask yourself:

• Do you just want expert feedback on your inventory or scope 3 calculations before publishing?
  • External review is a good next step.

The result: assurance

Assurance is the outcome of verification. After reviewing your data, the verifier issues a statement expressing their level of confidence.

Limited assurance: lower confidence, less detailed review - suitable for regulated disclosures.

Reasonable assurance: higher confidence, more detailed testing - suitable for investor or public reporting.

Ask yourself:

Which level of assurance (limited or reasonable) do I need?

• If your data supports mandatory or regulated reporting → Limited assurance
• If you are preparing investor-grade or public disclosures → Reasonable assurance

Why assurance matters now

In Australia, mandatory climate disclosures are being phased in under new sustainability standards from the Australian Accounting Standards Board (AASB), aligned with the International Sustainability Standards Board (ISSB). These require companies to obtain limited assurance over their GHG emissions data, with reasonable assurance expected in the future. The requirements will apply first to the largest listed and unlisted entities, then expand to smaller companies in later years.

In New Zealand, the Aotearoa New Zealand Climate Standards require limited assurance for climate disclosures, including scope 1 and 2 greenhouse gas (GHG) emissions, for climate reporting entities (listed issuers, large banks, insurers, and investment scheme managers). Over time, this is expected to progress to reasonable assurance. In addition, government departments covered by the Carbon Neutral

Other examples:

• Carbon markets (e.g. Australian Carbon Credit Units, Verra, Gold Standard) require independent verification and assurance of project emission reductions/removals.
• Some organisations voluntarily seek assurance of their GHG inventories or sustainability reports to meet investor and stakeholder expectations.
• Infrastructure projects and public procurement processes in both countries increasingly require assured carbon data to support business cases and funding.

“Audit” is a small word that causes a lot of confusion.

Some organisations say they’ve “audited” their carbon footprint when they’ve simply calculated it internally. In reality, “audit” has a very specific meaning in financial reporting - not GHG disclosure.

Audit: reasonable assurance over historical financial data.

Review: limited assurance over financial data.

For emissions data, the correct terms are verification, validation, or assurance under ISO 14064-3. Avoid using “audit” unless it truly fits that definition.

Where certification fits in

Certification goes a step further. It’s part of a formal scheme run by a government, industry body, or programme such as Toitū, Ekos, or Climate Active.

These schemes often require:

• verified emissions data
• an emissions reduction plan
• annual progress reporting
• commitments to wider sustainability goals

Ask yourself:

Are you claiming carbon neutrality or applying for a programme like Toitū, Ekos, or Climate Active?

• Certification is the right path, usually built on verified data.

Examples:

Australia: Climate Active certification shows a business has achieved net zero emissions.

New Zealand: Toitū and Ekos offer certifications for organisations and products.

Be transparent about what your certification covers - and what it doesn’t. (once published, link to: How to recognise credible certifications.

Using the right language

Clarity builds trust. Overstating what’s been done can unintentionally mislead stakeholders and risk accusations of greenwashing.

• Name the type of check (e.g. verified to ISO 14064-3)
• Include the provider’s name
• Avoid “audited” unless it meets audit definitions

Example wording:

“Our scope 1 and 2 greenhouse gas emissions for FY2024 were subject to limited assurance in line with ISO 14064-3 by [independent verifier].”

 
Recommendations

• Review emissions annually with an experienced third party.
• Choose verification over validation for more robust evidence.
• Stay across regulations - assurance is increasingly mandatory.
• Set a Science Based Target (SBT) after verification to keep progressing.
• Pick credible certification schemes and be transparent about their scope.