Search "best carbon accounting software" and most results give you a single ranked list. We build software too, so read our view with that bias in mind. A bank calculating financed emissions and an Australian group preparing an ASRS inventory need different things. This comparison groups tools by the work they are designed to handle, and it includes our own product.
"Best" depends on the reporting job
A single leaderboard hides the differences between buyers. Some organisations need financed-emissions reporting or one system spanning several disclosure regimes. Others need a consolidated ASRS inventory across Australian and overseas entities, whether they are building it for the first time or replacing an existing process. Start with your reporting obligations, the data you hold and the people who will run the work.
Match it to your situation
Four situations cover most Australian companies looking right now. Find yours, then read the section below it. Within each group the tools are listed in no particular order.
| If you are | Tools to consider | Why |
|---|---|---|
| A financial institution calculating financed emissions, or a group running a broad sustainability programme | Persefoni, Watershed, IBM Envizi | Financed-emissions capability or enterprise ESG data and reporting workflows |
| An Australian reporting group under ASRS, including multiple entities or overseas operations | CO2 Lab, Sumday, Avarni | Australian-built options with different workflows for ledgers, ERP data and source documents |
| Want an expert to own the methodology, for a complex or one-off year | A carbon consultant | Specialist support with the method, calculations and reporting process |
| Just exploring, or very small | A general-purpose AI, or a spreadsheet | Useful for early estimates and learning, but formal reporting needs stronger controls and evidence |
If you need financed emissions or several disclosure regimes
The large global platforms are designed for broad reporting programmes. Persefoni provides enterprise carbon accounting and disclosure, with particular depth in financed emissions aligned to PCAF. Watershed spans enterprise emissions measurement, multi-framework reporting and decarbonisation. IBM Envizi manages enterprise ESG data, emissions calculations and reporting. Before choosing one for a consolidated ASRS inventory, compare its implementation effort, data workflow and broader programme coverage with the work you need to complete. We cover each platform in Persefoni alternatives, Watershed alternatives, Workiva alternatives and Greenly alternatives.
If you're an Australian group reporting under ASRS
Australian ASRS reporting groups range from first-cycle reporters to experienced teams replacing a consultant or existing system. The three Australian-built tools use different workflows. Sumday uses a finance-led carbon ledger, with AI mapping, reporting, supplier engagement and training. Avarni combines enterprise integrations and AI-assisted data intake with local implementation. CO2 Lab, which we build, combines a carbon accounting platform with an AI Sustainability Analyst. Teams assign the data work to the analyst. It collects and processes the records, calculates emissions and prepares reporting outputs inside the platform. Your team reviews the working and judgement calls.
“A bank calculating financed emissions and an Australian group consolidating an ASRS inventory need different workflows, controls and implementation support.”
If you'd rather it was done for you
Software isn't the only route. A carbon consultant can bring methodology expertise and take responsibility for a complex first year or a one-off project. Your team will still need to supply records and answer questions, though the amount of internal work depends on the engagement. Software keeps more of the process in-house and can carry the method and data into the next reporting year. We compare the two approaches in consultant versus software.
How to test a shortlist
Shortlist two or three tools, then give each the same bill and ledger extract. Check the document calculation first. Then ask what has been counted, what is missing, what may be duplicated and how the result ties back to the ledger. Confirm that each figure shows its source, factor and reasoning. The full checklist is in how to choose carbon accounting software.
Where CO2 Lab fits. It combines a carbon accounting platform with an AI Sustainability Analyst for Australian ASRS reporting:
Keep reading
The no-names checklist in how to choose carbon accounting software, the consultant versus software trade-off, and, if you're doing this alone, ASRS reporting without a sustainability team.
Compare the workflow with your data
Bring a real bill and a ledger extract. The AI Sustainability Analyst does the data work, while the platform returns a review-ready ledger with the source, factor and reasoning behind each figure.
Book a Sustainability Check-up