Persefoni Diligent migration: your carbon accounting options when Diligent ESG moves to Persefoni

The short answer: on October 22, 2025, Diligent announced that it will move its carbon accounting clients from Diligent ESG to Persefoni's platform and take an equity stake in Persefoni. Neither company published a migration date. If your emissions inventory lives in Diligent ESG, you have three real options: accept the move to Persefoni, pick a different enterprise platform, or rebuild the inventory from your own accounts payable data in a ledger-first tool. The right one depends on your board setup, where your Scope 3 data sits, and whether your first California SB 253 report is due on November 10, 2026.

This is written for a US sustainability, finance or compliance lead whose company runs its carbon inventory in Diligent ESG and who has either heard about the Persefoni move from an account manager or read about it and now has to plan the next reporting cycle. Everything about Diligent and Persefoni below comes from the two companies' own announcements, Diligent's product and pricing pages and the Diligent One Platform help documentation. No prices appear, because neither company publishes one.

What did Diligent and Persefoni announce?

The joint announcement of October 22, 2025 says that "Diligent will transition its carbon accounting clients to Persefoni's market-leading platform" and that Diligent will "take an equity position in Persefoni." The stated reason is capability: Diligent's general manager for compliance, Amanda Carty, pointed to Persefoni's "advanced technology, compelling roadmap, and top-tier NPS among sustainability vendors," and the release promises Diligent clients "advanced Scope 3 supply chain sustainability solutions and AI-powered disclosure readiness."

Some context helps. Diligent is a governance, risk and compliance software company, best known for board portals. Its carbon product came from Accuvio, an Irish ESG reporting company it bought in August 2021. Diligent ESG calculates emissions mainly from fuel and energy consumption data using a library Diligent now puts at more than 70,000 factors across 120+ countries. Persefoni, by contrast, was built as a carbon accounting and climate disclosure platform from the start. In plain terms, a GRC vendor decided carbon calculation was better done by a specialist and chose one. The full product comparison is on Diligent ESG alternatives.

What the announcement does not tell you

A partnership release is written for investors and the press, not for the person who has to file. Four things that matter to you are missing from it.

When. No timeline was published. When we read Diligent's carbon accounting pages in September 2026, nearly a year later, they were still live and still described the Diligent calculation engine. You cannot plan a reporting year around a date nobody has given you.

How your history moves. A carbon inventory is more than totals. It is the activity data, the emission factor chosen for each source, the factor vintage, the boundary decisions and the evidence behind each figure. Two platforms with different factor libraries will not reproduce each other's numbers line for line, and a base year that cannot be reproduced is a base year you may have to restate. Our guide to setting an emissions baseline year covers when a recalculation is triggered.

What happens to the rest of Diligent ESG. The release is about carbon accounting clients. It does not say what happens to the qualitative ESG reporting and survey workflows many customers also run in Diligent, or how the two products will connect inside the Diligent One Platform beyond a general promise of integration.

What it costs. Diligent sells tailored packages through a form, and Persefoni quotes rather than publishing prices. Whether your carbon work will be billed by Diligent, by Persefoni or by both, and whether today's terms carry across, is a question for your contract, not for a press release.

Questions to ask Diligent before your carbon data moves

1. Which platform will calculate our fiscal 2026 inventory, and on what date does that change?
2. Can we export every activity record, the emission factor and factor source applied to each one, and the supporting evidence, in a format we can keep?
3. Will our base year and prior years be recalculated on Persefoni's factors, or carried over as reported? If recalculated, who explains the difference to our assurance provider?
4. Will our assurance provider have read access to the calculation trail on the new platform, and from when?
5. If our first SB 253 report is due November 10, 2026, which platform produces it?
6. Which contract governs the carbon work after the move, and do our current price and term carry over?

Get the answers in writing. If the first two cannot be answered clearly, export your data now regardless of which option you choose.

Persefoni Diligent migration: your three options compared

None of these is wrong. The mistake is drifting into the first one by default, because the migration is the moment a new evaluation is cheapest. You are already re-validating your data; testing an alternative on it at the same time costs very little. Persefoni itself is compared with the rest of the enterprise field on Persefoni alternatives.

Which option fits a US company with an SB 253 or CDP date?

Start from the calendar. Companies over $1 billion in revenue doing business in California owe their first SB 253 report, covering Scope 1 and Scope 2, by November 10, 2026, with Scope 3 from 2027 and limited assurance on Scope 1 and 2 phasing in. If your migration date is unknown and your filing date is not, the safe plan is the one that does not depend on a vendor project finishing in time. Our SB 253 90-day plan lays out the sequence, and SB 253 reporting software covers what the filing needs from a tool.

Next, look at where your footprint comes from. Diligent's documented input model is fuel and energy consumption data, which suits companies whose emissions are mostly Scope 1 and 2. For most US companies outside heavy industry, the larger share is Scope 3 purchased goods and services, and that data is already sitting in accounts payable. A migration that moves your energy data neatly but still leaves Scope 3 as a survey exercise has not solved the 2027 problem.

Finally, re-check your boundary while you are moving anyway. Whether a leased office or warehouse lands in Scope 1 and 2 or in Scope 3 category 8 depends on the lease and your control approach. If the only record of which sites you control is a stack of lease PDFs, pulling the key terms out of the commercial leases first gives both platforms the same boundary to work from, and makes any difference in totals easier to explain.

What to export from Diligent ESG this quarter, whatever you choose

• All activity data by site and period, with units.
• The emission factor, factor source and factor year applied to each record.
• Your organizational boundary and consolidation approach, including leased assets.
• Base year figures and any recalculation history.
• Supplier survey responses and the Scope 3 categories you reported or excluded, with the reasons.
• Any assurance statement and the sample your assurance provider tested.

With that file in hand, every option stays open, and the comparison between platforms becomes a comparison of numbers rather than of demos. If your Scope 3 is mostly spend, you can run our carbon accounting software on a few of your own AP lines at the top of this page and see the scope and category it proposes for each one before anything changes hands. The difference between limited and reasonable assurance, which decides how much of this trail you need, is set out in limited vs reasonable assurance for emissions.

Diligent and Persefoni facts on this page come from the October 22, 2025 partnership announcement published by both companies, Diligent's August 10, 2021 Accuvio acquisition release, Diligent's ESG, carbon accounting and pricing pages and the Diligent One Platform help documentation, read in September 2026. Details of the transition may change, so confirm them with Diligent and Persefoni directly. Diligent, Diligent One, Accuvio and Persefoni are trademarks of their respective owners; this page is not affiliated with, sponsored by or endorsed by either company.