Deleting The Receipts

When Acciona, the Spanish infrastructure group, issued green bonds in 2021 to finance renewable energy projects, the deal came with the usual documentation: a Green Financing Framework setting out how the proceeds would be used, and a Second Party Opinion (SPO) from Sustainalytics validating the framework’s credibility. Both documents were published online.

Try to find them using the original published links today. The framework URL leads to a server that no longer exists. The SPO returns the same result. At some point between late 2025 and early 2026, the hosting infrastructure was decommissioned and no redirects were put in place. Acciona, to its credit, has since republished both documents on its current website, but anyone following the links as originally distributed (in bond prospectuses, exchange filings, or SPO provider catalogues) will find them broken. The bonds are still trading.

Acciona is not unusual. And nobody did this on purpose.

Over the course of March and April 2026, I attempted to access 2,216 disclosure documents (SPOs and issuer Frameworks) for bonds still outstanding. Each was tested for public accessibility directly from its published URL, as any member of the public would attempt it. Where automated scripts could not reach a document due to website security measures, the page was tested manually, one by one, to avoid false positives.

The result: 510 documents, or 23.0 per cent of the total, could not be retrieved from their published URLs. These are associated with bonds representing roughly $672 billion in outstanding principal.

Nobody planned this. The pattern, as it emerges from the data, is one of inadvertent loss. Corporate websites are periodically rebuilt. Investor relations pages are reorganised. PDF libraries are migrated to new content management systems — or not. Sustainability disclosure documents, niche by nature, do not always survive the transition. The SPOs and Frameworks simply fall through the cracks.

The problem is not malice. It is that nobody is responsible for keeping these documents online. And so, quietly, they disappear.

The scale of the problem

Two documents are central to every labelled bond issuance. The Framework is the issuer’s own document, setting out eligible project categories, exclusion criteria and reporting commitments. The Second Party Opinion (SPO) is an independent assessment, typically from firms such as Sustainalytics, ISS ESG or S&P Global, evaluating the framework’s credibility.

The ICMA Green Bond Principles state that external reviews “should be made publicly available.” The EU Green Bond Standard, which came into force in 2024, goes further: reviewers “must” make assessments “freely available on their website” for the bond’s lifetime.

The gap between that expectation and reality is significant. Of the 925 Frameworks tested, 25.1 per cent were inaccessible. For the 1,291 SPOs, the figure was 21.5 per cent. Issuers are losing their own documents — the ones they wrote, published and used to market the bond — at a higher rate than the SPOs assessed by third parties. The pattern points to routine website maintenance as the primary driver: nobody set out to remove these documents, but nobody ensured they would survive the next site redesign.

A sharp threshold

The data reveals that document loss is not a gradual process. There is a distinct inflection point at the four-year mark, aligning with typical corporate website refresh cycles.

Documents less than three years old show a loss rate of roughly 13 per cent. At the four-year mark this jumps to 23 per cent, nearly doubling, before stabilising. The threshold aligns with typical corporate website refresh cycles. Documents that survive past it tend to sit on stable, purpose-built infrastructure. Those that do not were hosted on general-purpose corporate websites that nobody designed for long-term archival.

A systemic problem, not a bad actor problem

Of the 510 inaccessible documents, the overwhelming majority were not deliberately restricted. They were inadvertently lost. Some 424 returned a “not found” error — the classic symptom of a website rebuild that did not preserve legacy PDF links. A further 83 were blocked by website security measures that also prevent legitimate access. Only three sat behind paid subscriptions.

The issuer’s own website is the weakest link in the disclosure chain. More than 400 of the 510 inaccessible documents were hosted by the issuer themselves, not by an SPO provider. Corporate IT teams, reasonably, do not prioritise the preservation of niche PDF documents from bond issuances several years prior. Investor relations pages are redesigned. Content management systems are replaced. And the sustainability documents simply are not carried over.

This is not a story of bad actors. It is a story of a market that grew faster than the infrastructure to support it. Nobody set out to remove these documents from the public record. But the result is the same: a growing gap between the commitments that were made and the evidence that they were made.

What this means

A bond prospectus has regulatory requirements for its retention and public availability. A Green Bond Framework does not, despite being the document that defines the commitments which give the bond its label. When it disappears, there is no public record of what was promised. An issuer can update its framework, broadening eligible project categories or relaxing exclusion criteria, and no outside observer has a baseline against which to compare the revision.

The consequence is a growing information asymmetry. Institutional investors with terminal access and data subscriptions can still retrieve most of these documents through commercial aggregators. Individual investors, journalists, academics and civil society organisations cannot. The public record of what was committed is becoming available only to those who can afford to pay for it.

Bonds representing $672 billion in outstanding principal are associated with disclosure documents that cannot be found at their published URLs. The problem is structural. It is measurable. And on current trends it will get worse.

A growing regulatory risk

The disappearance of these documents is not merely a transparency problem. It is becoming a legal one. The EU Green Bond Standard (Regulation 2023/2631) explicitly requires that external reviews be published and remain “freely available” for the lifetime of the bond. Any issuer using the European Green Bond label whose Framework or SPO has been removed from public access is, on a plain reading, in breach of the regulation — regardless of whether the document happens to survive at some other URL.

In the UK, the Financial Conduct Authority’s anti-greenwashing rule (effective May 2024) requires sustainability-related claims to be “fair, clear, and not misleading” and “capable of being substantiated” for as long as the claim is being communicated. A green bond trading on the secondary market is an ongoing claim. If the underlying documentation cannot be accessed to verify that claim, the product may no longer meet the FCA’s requirements.

In Canada, amendments to the Competition Act (Bill C-59, 2024) introduced a reverse burden of proof for environmental claims: businesses must now demonstrate that claims are based on “adequate and proper substantiation in accordance with internationally recognised methodology.” An issuer whose Framework has been deleted during a website migration has destroyed its own substantiation.

These regulatory developments are recent, and enforcement is only beginning. But the direction is clear: what was once a voluntary disclosure norm is becoming a legal obligation. The market’s current approach of treating Frameworks and SPOs as temporary marketing materials — documents that can be lost in a routine website redesign — is increasingly at odds with the regulatory environment in which labelled bonds are now issued and traded.

The good news is that the fix is straightforward. Issuers should ensure that when websites are rebuilt, legacy PDF links are preserved or redirected. The industry should adopt a convention, similar to the DOI system used in academic publishing, that provides permanent, resolvable identifiers for disclosure documents. The XframeworkID registry was built with this objective.

Limitations

This is a point-in-time assessment conducted over March–April 2026. A document temporarily unavailable due to a server outage would register as permanently lost. Where automated scripts could not access a document due to website security measures, the page was tested manually to confirm true inaccessibility. The study population was drawn from the XframeworkID open registry, which does not cover the full labelled bond market. An estimated 700 or more additional SPOs exist behind paid subscriptions and are not reflected in the figures. The true inaccessibility rate is very probably higher than 23.0 per cent. A longitudinal study is needed.

A call for standards

ICMA, as the custodian of the Green Bond Principles, should consider strengthening its guidance from “should” to “must” on the public availability of Frameworks and external reviews, and should define minimum standards for document retention — including requirements for URL stability and redirects, or use of document resolvers like xframework.id.

Investors wishing to check the availability of disclosure documents for green bonds in their own portfolios can query the open registry at xframework.id.

For more details on this research or questions, please contact Ian Howard through the contact page on the xframework.id website.

Related literature

Existing research on green bond disclosure has focused on the quality and impact of external reviews rather than their physical persistence. Eugster, Schimdt and Zhao (2025) examine how SPO provider type affects disclosure quality, finding significant variation between specialist and generalist reviewers, but treat document availability as a given.⁴ The NBER working paper by Caramichael and Rapp (2024) argues that green labels often fund projects issuers would have undertaken anyway; the present study adds a new dimension to that critique by showing that even the documentation of those commitments is not being preserved.⁵

The Network for Greening the Financial System (NGFS) has identified transparency gaps as a barrier to effective green finance, noting that “clear and meaningful reporting underpins any effective external review.”⁶ The present study demonstrates that the problem extends beyond reporting clarity to the basic availability of the reports themselves.

⁴ Eugster, F., Schimdt, C. and Zhao, R. (2025). “The Role of External Reviews in the Corporate Green Bond Process.” Swiss Finance Institute Research Paper.
⁵ Caramichael, J. and Rapp, A. (2024). “The Green Bond Premium.” NBER Working Paper.
⁶ NGFS (2024). “Enhancing Market Transparency in Green and Transition Finance.”