Internal audit for the CO2 Performance Ladder: requirements from handbook 3.1
An internal audit is the check you carry out yourself on your CO2 management system, before the external auditor arrives. The CO2-Prestatieladder (CO2 Performance Ladder) handbook 3.1 requires you to do this at least once a year, covering the requirements that belong to your level. The requirements are in section 6.1.1.1 of the handbook 3.1 . For how the external assessment works, read the audit process. For what the auditor checks per point, see the audit checklist.
An internal audit is not a formality. The handbook uses it as a source for the management review and as a means to improve the system.
This page describes handbook 3.1. Handbook 4.0 was published on 14 January 2025, and 3.1 audits can still take place until 14 January 2027. Check with your certification body which version applies to your audit. See the transition arrangement .
What the handbook requires
Section 6.1.1.1 contains the core. In short, the requirements are:
- The internal audit is carried out at least once a year.
- The audit looks at the relevant requirements from the certification scheme, and at the objectives per requirement that belong to the target level.
- You make sure corrections and corrective actions are taken without undue delay, within a suitable timeframe.
- You check whether enough points have been achieved to keep your level.
- The results are recorded in an internal audit report.
- The auditor is objective and impartial, does not check their own work, and has relevant knowledge and skills.
- You record the process, planning, execution and responsibilities. The handbook partly bases these requirements on ISO 19011, the guideline for auditing management systems.
The handbook allows you to combine the internal audit with audits for other management systems, such as ISO 9001 or ISO 14001. That saves time, as long as the CO2 requirements clearly appear in the report.
How the audit relates to the management review
The internal audit is the main source of information for the management review (section 6.1.1.2). That review is the moment when management decides what changes. The internal audit provides the facts, and management chooses the measures. Without a good audit, management has nothing to base its decisions on.
The handbook also asks management to make resources for the audit available, such as time, training and an auditor who knows the CO2 Performance Ladder.
Step 1: plan the audit
Record what you will check, when and by whom. A simple plan for a small company:
| Requirement or part | Auditor | Week | Evidence you check |
|---|---|---|---|
| 2.A energy flows | Office manager | Week 12 | List of energy flows, invoices |
| 2.B reduction target | Quality manager | Week 13 | Target, management report |
| 2.C communication | Quality manager | Week 13 | Internal newsletter, management cycle |
| 3.A emission inventory | External auditor (fictional) | Week 14 | Inventory report |
Note: the auditor may not assess their own work. If the office manager manages the energy flows, someone else checks that list. In a small company this can be difficult. Then you hire an external auditor, or you exchange auditors with a comparable company.
Step 2: ask the questions per requirement
The handbook is clear here. For each objective per requirement (1.A, 2.A, and so on), you answer three questions:
- Does the organisation find that its activities are making progress towards the objective?
- What evidence supports this?
- Which decisions does management need to make about additional or corrective measures?
The handbook is emphatic: it is not enough to report that the objective is met. You must write out, for each requirement, how you answer the three questions.
Example for requirement 2.B.1
A fictional construction company has this objective: “Over two years, the vehicle fleet uses less diesel per unit of turnover.” The internal auditor then writes:
- Progress: Diesel consumption per construction site fell by a few percent in the first half year, according to the fuel card data. That is an indication, not a final conclusion.
- Evidence: Fuel card statements for the first six months, compared with the same period last year. The number of construction sites is included, because it affects the figure.
- Decision for management: Replace the fleet of two vans with one hybrid bus, or tighten the route planning per construction site.
An answer like this shows that the auditor has thought it through and that management has a decision to make. “Objective is being met” does not show that.
Step 3: record the report
The internal audit report contains at least:
- The date of the audit.
- The names of the auditor(s) and the auditee(s).
- The objective of the audit.
- The scope.
- The locations visited.
- The audit findings.
- Conclusions per requirement on whether the objective is met.
- The effectiveness of the system in relation to improving CO2 and energy performance and achieving the reduction targets.
A report that only lists findings, without conclusions per requirement, does not comply. The LadderCI (the body that assesses the CO2 Performance Ladder) will look at this during the external assessment.
Step 4: check the points
The handbook asks you to check whether you achieve enough points to keep your level. You calculate the scores per requirement and perspective, and check whether you exceed 90% of the maximum. If the calculation falls below that limit, you plan measures before the external assessment.
That check is not just a formality. It prevents you from being surprised by a lower score at the annual ladder assessment.
Common mistakes in the internal audit
The audit is a form. Items are ticked off without anyone looking at practice. The auditor does not look at evidence and does not ask questions.
The auditor checks their own work. The handbook explicitly excludes this. It also produces a weak report, because nobody assesses themselves critically.
No follow-up. The audit finds a shortcoming, but nobody turns it into an action. The handbook asks for corrections without undue delay.
Only “meets” in the report. It is not enough to report that the requirement is met. You answer the three questions per objective.
No link to the management review. If management does not discuss the findings and no decision follows, the purpose of the audit is lost.
What does the auditor want to see?
- An annual plan for the internal audit with the requirements per level.
- An internal audit report with all mandatory parts.
- An answer to the three questions for each requirement.
- A follow-up list with actions, owners and dates.
- The management review report, which ties in with the audit.
How the internal audit fits into the whole process
The internal audit comes after preparation and before the external assessment. Read the audit checklist to see which evidence you need, and the step-by-step plan to keep the order on track. For the external side of the story, including what the LadderCI does, see the audit process.
If you are not sure which requirements apply to your level, start with the requirements of the ladder. The four perspectives are explained there.