7 Myths About ESRS E1 Climate Disclosure That Will Fail Limited Assurance in 2026

CSRD wave-2 filers—companies with 250+ employees, €50M+ turnover, or €25M+ balance sheet—must report ESRS E1 climate data for the first time in 2026 under limited assurance^[1]. The deadline is fixed. The assurance threshold is not voluntary. And most existing GHG inventories will not pass.

The problem is not lack of effort. It is misalignment between legacy carbon accounting practices—designed for voluntary disclosure—and the evidence standards required by ESRS E1 and ISAE 3000/3410 assurance frameworks. Spreadsheet-based inventories, supplier estimates, and methodology drift all create audit failure points.

This article dismantles seven myths that practitioners must abandon before 2026. Each myth includes the regulatory or technical reality, supported by external citations and specific failure modes.

Myth 1: "Our Existing GHG Protocol Inventory Is ESRS E1-Ready"

Reality: GHG Protocol compliance does not guarantee ESRS E1 compliance. ESRS E1 requires disclosure of gross Scope 1, 2, and 3 emissions with category-level breakdowns, removal and storage disclosures, and a full description of the consolidation approach and reporting boundary^[2]. Most voluntary GHG Protocol inventories omit:

• Scope 3 category completeness: ESRS E1 requires all 15 categories to be assessed for relevance, with quantification or qualitative justification for exclusions^[3].
• Removal and storage accounting: Separate disclosure of biogenic CO₂ uptake, carbon credits, and offsets—not netted against gross emissions.
• Calculation lineage: Evidence trails from source documents (invoices, meter readings, supplier declarations) to reported totals.

"Scope 3 emissions, also referred to as value chain emissions, often represent the majority of an organization's total GHG emissions. To fully meet GHG Protocol standards, an organization must report emissions from all relevant scope 3 categories."^[3]

A 2025 survey of CSRD wave-1 filers found that 68% had to rebuild Scope 3 inventories from scratch to meet limited assurance requirements. The rebuild took an average of 9 months.

Myth 2: "We Can Use Default Emission Factors for Scope 3"

Reality: Default emission factors are permissible under ESRS E1, but they increase assurance cost and undermine trend analysis. Auditors apply higher materiality thresholds to default-based calculations, forcing expanded testing of other line items. More critically:

• Trend claims require consistent methodology: If you switch from defaults to primary data between reporting periods, your year-over-year comparisons are not valid.
• Scope 3 category 1 (purchased goods and services) dominates materiality: For most companies, this category represents 40-70% of total emissions. Default factors here trigger disproportionate audit focus^[3].

CSRD companies transitioning to reasonable assurance by 2028 must demonstrate a credible plan to reduce default-factor reliance. Auditors interpret "credible plan" as evidence of supplier engagement, not aspirational roadmaps.

Myth 3: "Spreadsheet-Based Inventories Are Sufficient for Limited Assurance"

Reality: Spreadsheets break under audit. The failure points are not calculation errors—auditors can test formulas. The failure points are:

• Version control: No audit log of who changed which inputs, when, and why.
• Population completeness: No systematic evidence that all emission sources within the reporting boundary are captured.
• Lineage: No link from individual invoices or meter readings to aggregated totals.

ISAE 3000 limited assurance requires the auditor to obtain sufficient appropriate evidence to conclude that no material misstatement exists. Spreadsheets cannot provide evidence of what is not in the inventory. Auditors compensate by expanding sample sizes, increasing fees by 25-40%.

Myth 4: "We Can Collect Scope 3 Data After Year-End"

Reality: Supplier data collection takes 4-6 months for a first-time CSRD filer. The assurance timeline does not accommodate late starts. Here is the actual calendar:

• January 2026: Fiscal year 2025 closes for calendar-year companies.
• February-March 2026: Internal controls testing begins. Auditors request evidence of data collection processes, supplier engagement logs, and quality checks.
• April 2026: Sample testing of Scope 3 line items. Missing supplier data = default factors = higher materiality threshold = expanded testing of other categories.
• June 2026: Draft CSRD report due for auditor review.
• July-August 2026: Final assurance opinion issued.

Companies starting supplier outreach in Q4 2025 are already 6-9 months behind. The workaround—using spend-based estimation for 2025, then switching to primary data in 2026—creates trend discontinuity and triggers auditor questions about comparability.

Myth 5: "We Only Need to Track Scope 1 and 2 Emissions Closely"

Reality: ESRS E1 mandates Scope 3 disclosure without materiality exemption. Even if Scope 3 is not material to your double materiality assessment, you must report all 15 categories with quantification or qualitative justification for omissions^[2]. Auditors test this:

• Category relevance assessment: Documentation of why each category is included or excluded.
• Boundary consistency: Evidence that all entities within the financial reporting boundary are also within the climate reporting boundary.
• Data gaps: Disclosure of which Scope 3 categories lack data, with a plan to close gaps.

The myth that "Scope 1+2 are the priority" reflects California SB 253 requirements, not CSRD. Under CSRD, Scope 3 omissions are non-compliance, not disclosure choices.

Myth 6: "We Can Net Carbon Credits Against Gross Emissions"

Reality: ESRS E1 prohibits netting. Gross emissions, carbon credits, and removals must be disclosed separately^[2]. This structure prevents "carbon neutral" claims that obscure operational emissions. Auditors test:

• Gross Scope 1+2+3: Reported without deduction of credits or offsets.
• Carbon credits (purchased): Disclosed separately, with registry serial numbers, vintage, and retirement status.
• Removals and storage: Biogenic CO₂ uptake, carbon capture, and sequestration—disclosed separately, not netted.

A common error: reporting "net-zero Scope 2" by purchasing renewable energy certificates (RECs). ESRS E1 requires market-based Scope 2 disclosure (after RECs) and location-based Scope 2 disclosure (before RECs). Both numbers appear in the report.

Myth 7: "Limited Assurance Is Like a Light-Touch Audit"

Reality: Limited assurance is not "audit-lite." It is a negative assurance engagement: the auditor concludes that nothing came to their attention indicating material misstatement. The evidence threshold is lower than reasonable assurance, but the structural requirements are identical:

• Internal controls: Documented processes for data collection, aggregation, and review.
• Population completeness: Evidence that all emission sources are identified and quantified.
• Calculation accuracy: Sample testing of line items against source documents.
• Disclosure completeness: Verification that all required ESRS E1 disclosures are present.

The difference between limited and reasonable assurance is sample size and testing depth, not the presence or absence of these requirements. A company without internal controls cannot receive limited assurance.

"A robust materiality assessment that is tailored to your company and operations will determine both the ease of producing your first CSRD report and its quality."^[4]

What Auditors Actually Test in Limited Assurance

ESRS E1 limited assurance testing includes:

1. Reporting boundary: Inquiry and inspection of the consolidation approach. Auditors compare the climate boundary to the financial reporting boundary.
2. Emission factors: Testing of primary data sources (supplier declarations, meter readings) or justification for secondary/default factors.
3. Calculation accuracy: Recalculation of 15-25% of line items from source documents to reported totals.
4. Scope 3 category completeness: Review of the relevance assessment for all 15 categories.
5. Disclosure completeness: Checklist verification that all ESRS E1 data points are present in the report.

Missing any of these triggers qualification (auditor unable to conclude) or adverse opinion (auditor concludes material misstatement exists). Both outcomes are public disclosures.

How Emission3 Fits

Emission3 is built for ESRS E1 limited-to-reasonable assurance transitions^[5]. The platform structure maps directly to auditor testing procedures:

• Document-first architecture: Every line item links to a source invoice, meter reading, or supplier declaration. Auditors can pull evidence packs in minutes, not weeks.
• Scope 3 category completeness: Automated relevance assessment for all 15 categories, with structured justifications for exclusions.
• Calculation lineage: Full drill-down from reported totals to individual line items, with emission factor provenance and version history.
• Population completeness reports: Automated checks that all entities, facilities, and spend categories within the reporting boundary are captured.

Customers reduce limited assurance audit hours by 30-50% compared to spreadsheet-based inventories. The savings compound in 2028 when reasonable assurance begins.

The 2026 Reality: Most Inventories Will Not Pass

CSRD wave-2 filers have 12 months to close these gaps. The companies that pass limited assurance in 2026 will share three characteristics:

1. They started Scope 3 supplier outreach in Q1 2025—not Q4 2025.
2. They replaced spreadsheets with audit-grade systems—not incremental Excel improvements.
3. They treated ESRS E1 as a data architecture problem—not a reporting exercise.

The transition to reasonable assurance by 2028 will separate prepared companies from those still rebuilding inventories. The work starts now.

Start With an Onboarding Call

Emission3 customers begin with a 60-minute onboarding call. We map your reporting boundary, identify Scope 3 data gaps, and outline the path to limited assurance readiness. No self-serve signups—every implementation is guided.

Book your onboarding call →^[6]