Sustainability-Linked Loan Verification: The Complete Guide

What is SLL verification?

In a Sustainability-Linked Loan, economic terms (typically the margin) move with the borrower's sustainability performance. SLL verification is the process that confirms whether that performance actually happened as reported. A qualified party, independent of the borrower, reviews the KPI data, the calculation method and the underlying evidence, then issues a conclusion on whether each SPT was met.

The term is used for two different activities that are often confused: a review during structuring (before or at signing) and performance verification during the life of the loan. Both are forms of external review, but they answer different questions. This guide covers both and explains how they connect.

See also: What is a Sustainability-Linked Loan?

Why is verification used in Sustainability-Linked Loans?

Pricing depends on reported data. Without an independent check, the margin mechanism would rely on the borrower assessing its own performance. Verification protects the credibility of the instrument for three groups: lenders, who need a defensible basis for applying or refusing a margin adjustment; borrowers, who need their sustainability claims to withstand scrutiny; and the wider market, which relies on SLLs not being used for greenwashing.

Verification is one of the five core components of the Sustainability-Linked Loan Principles (SLLP), published by the LMA, APLMA and LSTA. The SLLP are voluntary market principles, not law. They become binding on the parties only to the extent they are written into the facility agreement.

KPIs, SPTs and baselines: what is actually verified

Every SLL verification is anchored in three defined elements in the loan documentation.

See also: KPIs and SPTs in SLLs

What evidence is reviewed?

The verifier tests reported KPI values against source evidence. Typical evidence includes:

• Source data: meter readings, utility and fuel invoices, energy supplier statements, production records
• Calculation workbooks, emission factors and conversion factors, with their sources and versions
• The methodology document agreed in the facility, including scope and organisational boundary
• Records of changes in scope, structure or methodology during the period
• Internal controls over data collection, and sign-offs by data owners
• Prior period reports and verification conclusions, for consistency

See also: Documents required for SLL verification

External review during structuring and the Second Party Opinion

Before or at signing, the borrower may obtain an external review of the SLL structure. In the sustainable finance market this is commonly delivered as a Second Party Opinion (SPO). It assesses whether the KPIs are relevant and material, whether the SPTs are ambitious and credible, and whether the overall structure aligns with the SLLP.

Under the SLLP, a pre-signing external review is recommended rather than universally required; lenders and borrowers decide whether to obtain one. An SPO does not verify performance. It assesses design. Performance verification comes later.

See also: Second Party Opinion vs annual SLL verification

Annual verification of SPT performance

After signing, the borrower reports KPI performance for each reporting period. The SLLP state that borrowers should obtain independent and external verification of their performance level against each SPT for each KPI, at least once a year. In practice this is usually a limited or reasonable assurance engagement, often performed under ISAE 3000 (Revised) by an audit firm, or a verification by a specialist sustainability or technical provider, depending on what the facility agreement specifies.

The verification conclusion is then delivered to the lenders, usually with the borrower's sustainability compliance certificate, and drives the margin adjustment mechanism.

See also: What external verification means in an SLL

Reporting

Reporting and verification are linked but distinct. The SLLP expect borrowers to provide lenders, at least annually, with up-to-date information sufficient to monitor SPT performance. The facility agreement usually defines the format (often a compliance certificate), the deadline after the period end, and which verification report must accompany it. Public disclosure is encouraged by the SLLP but is not always contractually required.

Borrower responsibilities

Responsibilities come from the facility agreement, so they vary. In common market practice the borrower is responsible for:

• Collecting and calculating KPI data on the agreed methodology and boundary
• Appointing a verifier that meets the qualifications set in the agreement
• Giving the verifier access to data, systems and people
• Flagging events that may trigger a baseline recalculation
• Delivering the report and certificate to the agent or lenders on time

See also: SLL borrower checklist, For borrowers

The lender perspective

Lenders rely on the verification report to apply the margin adjustment and to support their own sustainable finance disclosures. They typically check that the verifier is independent and qualified as agreed, that the scope of the conclusion covers every KPI and SPT, that the assurance level matches the contract, and that any qualifications or limitations are understood. For banks running many SLLs, consistency of verification across the portfolio is as important as the quality of any single report.

See also: For financial institutions

Why independent verification matters

Independence is what gives a verification conclusion value. A verifier must not have prepared the data it verifies, must not have a financial interest in the outcome, and must manage any other relationship with the borrower. Who qualifies, and how conflicts are handled, is covered in detail in our guide on who can verify a Sustainability-Linked Loan.

See also: Who can verify a Sustainability-Linked Loan?

The verification lifecycle of an SLL

Across the life of a facility, verification usually follows this sequence:

• Structuring: KPIs, SPTs, baselines and methodology are defined; optional pre-signing external review or SPO
• Signing: verification requirements (frequency, verifier qualifications, assurance level, deadlines) are fixed in the facility agreement
• Data collection: the borrower gathers evidence during each reporting period
• Annual performance verification: the independent verifier tests KPI data against each SPT
• Reporting: the verification report and compliance certificate go to the lenders
• Margin adjustment: the agreed pricing consequence is applied
• Recalculation and repeat: baselines are adjusted where the agreement allows, and the cycle repeats until maturity

See also: How Audelya supports this workflow

Legal requirements, contractual terms and market practice

It helps to separate the sources of obligation. There is currently no general legal requirement that defines SLL verification. Obligations to verify come from the facility agreement. The SLLP are voluntary market principles that most SLLs reference. Methodologies such as ISAE 3000 are professional standards applied by assurance providers. Many other features described above, such as evidence packages and timelines, are common market practice rather than rules.

Audelya's own approach sits on top of these: a structured workflow that connects borrower, lender and independent verifier, with AI-assisted evidence checks and a full audit trail. Final verification conclusions remain with the qualified human verifier.