When do I have to move to Handbook 4.0 of the CO2 Performance Ladder?

You can be audited against Handbook 3.1 until 14 January 2027. Your first audit after that date must be a 4.0 audit. The last valid 3.1 certificate expires no later than 14 January 2028, 36 months after version 4.0 was published on 14 January 2025.

Is a 3.1 certificate valid in a tender based on version 4.0?

No. SKAO states that a version 3.1 certificate is not valid in a tender based on version 4.0. The reverse works, but only during the transition period: a 4.0 certificate at step 1 is accepted as evidence of CO2 ambition level 3, and step 2 or step 3 as evidence of ambition level 5. From 14 January 2027 SKAO advises contracting authorities to stop using version 3.1.

Which step in version 4.0 matches my current level 4?

Old level 4 has no clean successor. Step 1 is accepted where level 3 is asked for, and steps 2 and 3 where level 5 is asked for. The acceptance table in the SKAO FAQ also counts a step 2 certificate as a level 4 and 5 certificate, but no step inherits the content of level 4. Organisations at level 4 choose between dropping back to step 1 or climbing to step 2, with a climate transition plan, a value chain analysis and an OBE analysis.

What can I reuse from my 3.1 documentation?

Your scope 1 and 2 emission inventory, your action plan with measures, your management review and your internal audit largely carry over. The energy review, your targets and your communication plan need adjustment. New or fully rewritten are the scope 3 ranking, the value chain analysis, the analysis of other influenceable emissions (OBE), the climate transition plan and the inclusion of non-CO2 greenhouse gases.

What exactly changed from version 3.1 to version 4.0?

The five levels were replaced by three steps. The scope of the energy review rises from 80 to 90 percent of energy use. The lower bound for quantifying scope 3 moves from 70 to 80 percent to two thirds. Business travel leaves scope 1 and 2 and becomes a mandatory scope 3 category from step 2. The location based scope 2 footprint is new. Non-CO2 greenhouse gases become mandatory where relevant. The climate transition plan and the OBE analysis are entirely new.

Is the first audit against version 4.0 an annual audit or an initial audit?

The transition arrangement states that organisations holding a valid 3.1 certificate who have a 4.0 audit for step 1 may continue their 3.1 audit cycle. For step 2 and step 3, 4.0 audits are always an initial audit. That makes the move to step 2 heavier and more expensive than the extra documentation alone.

Who has to align the climate transition plan with an independent expert?

At step 2, SKAO states that large organisations with more than 250 employees must align their climate transition plan with an independent expert and discuss it twice a year with a chain partner. At step 3, small organisations with fewer than 250 employees do not have to discuss their climate transition plan with an independent expert. It is alignment and dialogue, not an assessment.

Does the way my organisation size is determined change in version 4.0?

Yes. SKAO's list of changes states that size is determined on headcount, turnover and balance sheet total, the same criteria used for the CSRD, instead of on scope 1 and 2 emissions. Organisations can therefore land in a different size class, which affects both the requirements and the number of audit days.

From when do Rijkswaterstaat and ProRail use Handbook 4.0?

Rijkswaterstaat applies Handbook 4.0 to procurements published on TenderNed after 1 July 2026, with a notional discount of 2 percent at step 1, 4 percent at step 2 and up to 6 percent at step 3. Procurements published before that date stay under Handbook 3.1, and a 4.0 certificate offered there is valued on the levels from Handbook 3.1. ProRail moves to Handbook 4.0 for new TenderNed notices from 1 January 2027.

From 3.1 to 4.0: what you can reuse and what you have to rewrite

Q: Do I need one more 3.1 audit before 14 January 2027?

Only if you genuinely use that year to prepare step 2. A 3.1 certificate obtained in late 2026 expires no later than 14 January 2028, so you pay for three years and use about one. If you bid for Rijkswaterstaat or ProRail work, their procurement calendar sets your date.

Last updated: 11 August 2026 · Palau

You can be audited against Handbook 3.1 until 14 January 2027. Your next audit after that is a 4.0 audit. Footprint, energy review and measures largely carry over. New: the climate transition plan, other influenceable emissions (OBE) and non-CO₂ greenhouse gases.

Last updated: 11 August 2026. Author: Palau.

The CO₂ Performance Ladder (CO₂-Prestatieladder) is a Dutch and Belgian certification scheme used by public buyers as a tender award criterion. A sustainability lead summed the migration up like this: "We are ready to do the audit following the 3.1 handbook, but we do not have the new demands in the handbook." Data collected, measures defined, action plan finished, and then 4.0 asks for things that are not in that pack. Most of the work carries over. What does not stays invisible until you go looking for it.

When do I have to move to Handbook 4.0?

SKAO, the scheme owner, published Handbook 4.0 on 14 January 2025 and gave the market three years. The Ladder is used by more than 8,000 organisations, all of which have to move. Four dates set your room to manoeuvre.

Date	What happens	What it means for you
14 July 2025	Certification bodies may run 4.0 audits, once accredited by RvA (NL) or BELAC (BE)	From here you can certify against 4.0
14 January 2026	Earliest date SKAO advises buyers to use 4.0 as an award criterion	A market date binding the buyer. You may start meeting 4.0 in tender documents
14 January 2027	Last possible 3.1 audit. After this SKAO advises buyers to stop using 3.1	Your first audit after this is a 4.0 audit. No extensions
14 January 2028	Final expiry of 3.1 certificates, 36 months after 4.0 was published	After this no valid 3.1 certificate exists

Source: the Overgangsregeling, SKAO's transition arrangement: valid 3.1 certificates can exist until 14 January 2028, "36 maanden na de publicatiedatum van Handboek 4.0".

Two buyers often set the real pace. At Rijkswaterstaat, the Dutch national infrastructure agency, Handbook 4.0 applies only to procurements published "na 1 juli 2026", with a notional discount of 2% at step 1, 4% at step 2 and up to 6% at step 3 (Infrasite). ProRail, the rail infrastructure manager, moves to 4.0 on 1 January 2027, with an advantage that rises with the ambition level. Bid to either regularly and your real deadline sits well before 14 January 2027.

I already hold a 3.1 certificate, how long do I have?

Your certificate stays valid until your next audit. Audits against 3.1 remain possible until 14 January 2027, and the transition arrangement is literal about what follows: "Deze certificaten blijven geldig tot de eerstvolgende (jaarlijkse) audit." Your own audit calendar decides when you switch.

The type of audit differs by step, and that difference costs money. On step 1, holders of a valid 3.1 certificate "mogen hun 3.1-auditcyclus voortzetten" and keep their existing cycle. On the higher steps: "4.0-Audits voor trede 2 en 3 zijn altijd een initiële audit." Your certification cycle restarts. Budget that full initial audit when you cost the Ladder.

Watch the audit day table (auditdagentabel) too. Your size class is now set "op basis van FTE, jaaromzet en balanstotaal; dezelfde criteria die voor de CSRD gehanteerd worden" (Wijzigingenlijst): headcount, turnover and balance sheet total, the same criteria the CSRD uses, instead of scope 1 and 2 emissions. Our own inference, which SKAO does not spell out: low emissions with high headcount or turnover can push you into a larger class, with more requirements and more audit days.

Is a 3.1 certificate valid in a 4.0 tender?

No. The SKAO FAQ is explicit: "Nee, een certificaat voor versie 3.1 is niet geldig in een aanbesteding op basis van versie 4.0." The reverse works, and only for now: "In de overgangsperiode (...) kunnen 4.0-certificaten worden geaccepteerd in een aanbesteding op basis van Handboek 3.1."

You hold	Tender asks for 3.1 (transition period only)	Tender asks for 4.0
3.1 certificate, level 3	Valid, counts as level 3	Not valid
3.1 certificate, level 5	Valid, counts as level 5	Not valid
4.0 certificate, step 1	Valid, accepted as evidence of CO₂ ambition level 3	Valid, step 1
4.0 certificate, step 2 or 3	Valid, accepted as evidence of CO₂ ambition level 5	Valid, step 2 or step 3

The middle column has an expiry date. That acceptance applies "in de overgangsperiode", and from 14 January 2027 SKAO advises buyers to stop using 3.1 altogether. A 4.0 certificate works in both columns today, a 3.1 certificate in one, and that channel is closing. Rijkswaterstaat adds a detail: "De waardering vindt dan plaats op basis van de niveaus uit Handboek 3.1." On older procurements your step is converted back to the old level before it is scored.

Why that matters commercially: the Ladder is used as a gunningvoordeel, a tender award advantage. Your bid price is notionally reduced for evaluation only, as a fictieve korting (notional discount), a fixed amount or points. If you win you are paid the full price you quoted, and a higher certified step buys a larger reduction. More in tender advantage with the CO₂ Performance Ladder.

Which step matches my current level?

Version 4.0 has three steps (treden), not five levels (niveaus). SKAO maps them to the old levels in four of its own publications, in four different ways.

Source	What it literally says
SKAO FAQ, body text	Step 1 "wordt geaccepteerd als bewijs voor CO₂-ambitieniveau 3", step 2 or step 3 "wordt geaccepteerd als bewijs voor CO₂-ambitieniveau 5"
SKAO FAQ, acceptance table	Step 1 "geaccepteerd als een certificaat Niveau 1, 2 en 3 van Handboek 3.1". Steps 2 and 3: "Niveau 4 en 5 van Handboek 3.1"
Overgangsregeling 3.1 to 4.0	"Handboek 4.0-Trede 1 wordt geaccepteerd als Handboek 3.1 Niveau 3". Steps 2 and 3: level 5
SKAO blog on tendering	"'Gelijkstaat' is niet helemaal de juiste term." The advice: value step 1 at least as highly as level 3, and steps 2 and 3 at least as highly as level 5

The four wordings point the same way without covering each other. The FAQ body text names only ambition levels 3 and 5. Its acceptance table folds levels 1 and 2 into step 1 and level 4 into steps 2 and 3. The transition arrangement gives one level per step. The tendering blog refuses the word "equals" altogether. For your bid this makes little difference, for your ambition choice it does.

Because old level 4 has no clean successor. It was the qualitative middle rung where scope 3 entered, through a ranking of material emissions and two chain analyses. As an ambition step it is gone. A step 2 certificate is accepted against a level 4 requirement in a running 3.1 tender, per the FAQ, but no step inherits the content of level 4. At level 4 you choose between dropping back to step 1 or climbing to step 2, and that is the only decision in this migration that really matters. More in why there are now three steps, not five levels.

Do I need one more 3.1 audit before 14 January 2027?

Three questions, in order.

Question 1. Do you bid for Rijkswaterstaat, ProRail, or Flemish infrastructure contracts from five million euro upward? Yes: their calendar sets your date. Move to 4.0 as soon as you can and skip a last 3.1 audit. Go to question 3. No: go to question 2.

Question 2. Does your certificate run past 14 January 2027? Yes: you switch at your first audit after that date anyway, and an extra 3.1 audit buys no extra validity. Go to question 3. No: you choose between recertifying under 3.1 or moving straight to 4.0. A 3.1 certificate issued in December 2026 expires no later than 14 January 2028: you pay for three years and use one. Go to question 3.

Question 3. Which level are you on now?

Where you are	Target in 4.0	Practical advice
Level 1 or 2	Step 1	Deleted in 4.0. Step 1 sits at old level 3. Start now, you have the least to reuse
Level 3	Step 1	Switch at your 2026 audit. SKAO expects "de meeste bedrijven" at level 3 to reach step 1 "met vergelijkbare inspanning", with comparable effort. An expectation about most firms, not a guarantee for yours. The audit can stay annual
Level 4	Step 1 or step 2	No successor, so you must choose anyway. Do one more 3.1 audit only if you use that year to build step 2
Level 5	Step 2	Your chain analyses are not enough. Plan step 2 as an initial audit and start a year before the audit date

Source: SKAO FAQ.

What exactly changed from 3.1 to 4.0?

The structure stays more recognisable than most summaries suggest. The four angles (invalshoeken) A, B, C and D return in 4.0: part 2 of the certification scheme works with "maximaal 10 punten per eis, waarvan er minimaal 7 gehaald moeten worden en minimaal 90% van de punten per invalshoek", so 10 points per requirement, at least 7 scored, and at least 90% per angle. SKAO does not say how that compares to the weighting in 3.1, so do not assume your old score distribution carries over.

The shifts that do not attach to a single document, from SKAO's own list of changes:

Topic	3.1	4.0
Business travel	Inside scope 1 and 2	Out of scope 1 and 2. A mandatory scope 3 category from step 2
Lower bound for quantifying scope 3	70 to 80%	Two thirds
Reporting frequency	Every six months	Annual
Correction period, minor non-conformity	3 months	12 months

Source: Wijzigingenlijst 4.0 en 3.1, publication version 1.0.

Reporting frequency is one of the few places where 4.0 reduces your workload.

What can I reuse and what do I have to rewrite?

The status column refers to the document as it sits on your drive today.

What you have now	Status in 4.0	What actually has to happen
Emission inventory, scope 1 and 2	Reuse	ISO 14064-1 and the GHG Protocol still apply. Business travel out, location based scope 2 in
Non-CO₂ greenhouse gases	New	Mandatory in scope 1 and 2 where relevant, reassessed every three years
Energy review	Adjust	Coverage from 80% to 90% of energy use, plus an energy balance and flexibility in the energy system
Action plan with measures	Reuse	The list stands. New is an explicit choice between hitting your targets or delivering your measures
Short term targets	Adjust	May run for 1, 2 or 3 years, set against your previous target instead of a fixed three year cycle
Energy saving and renewable energy targets	Adjust	More emphasis on saving energy as a strategy, alongside renewable sources
Communication plan	Adjust	More freedom over what you publish on your website. Key personnel become a mandatory audience
Evidence of participation in chain initiatives	Reframe	Participation is no longer mandatory. Required instead: an analysis of your knowledge and collaboration needs
PMC analysis (product market combination) and scope 3 ranking	Rewrite	Replaced by a breakdown into activities across scope 1, 2 and 3, at a 50% threshold
Chain analyses from level 4 or 5	Mostly rewrite	Data and calculations stay usable, the document does not meet the value chain analysis requirements
OBE analysis	New	Other influenceable emissions: emissions outside the chain that still result from your activities, such as reused materials or shared energy. Qualitative at step 2
Climate transition plan	New	Mandatory from step 2, with a medium term reduction strategy. At step 2, "grote organisaties (meer dan 250 werknemers)" must have it "afgestemd met een onafhankelijke deskundige", aligned with an independent expert, plus twice yearly discussion with a chain partner. At step 3, organisations under 250 employees are exempt. Dialogue, not an assessment
Management review and internal audit	Reuse	Stays, and fits ISO 9001 and 14001 better under the Harmonized Structure
Size class	Redetermine	Not on emissions but on headcount, turnover and balance sheet total

Sources: the Wijzigingenlijst 4.0 en 3.1, and Alles over trede 2 en 3 for the climate transition plan, the OBE analysis and the 250 employee threshold.

Seven of the fourteen rows are reuse or adjustment, eight counting the reframed participation evidence. The work sits in the five rows that are new or have to be rewritten. Four are on the value chain and strategy side: the ranking, the value chain analysis, the OBE analysis and the climate transition plan. The fifth is your size class, administrative but decisive for how many audit days you get.

Write a climate transition plan so it also serves your ESRS E1 obligation. That bridge was built deliberately and is described in the CO₂ Performance Ladder and CSRD: one dataset, two reports.

Why does this migration feel easier than it is?

Almost nobody has gone first. Very few contractors have migrated, so there is no reference implementation to copy. For 3.1 there are over 1,200 published chain analyses in SKAO's library. For 4.0 that library does not exist.

Sector templates are missing too. A sustainability lead: "We now generate our own format. But I am not sure if it is in line with what the auditor expects." No settled shape exists yet for a climate transition plan a Ladder auditor accepts.

Then there is the vocabulary. Practitioners report auditors who are, in their words, allergic when you say level where step belongs. The wording gives away within two minutes whether you have read the new handbook. Use "step" consistently once you are on 4.0, including in file names.

The calendar does not help. Most audits cluster around December, March and the first quarter, and preparation running through July and August loses weeks to the construction holiday and to three week absences that do not overlap. Start a step 2 migration in May for a September audit and you effectively have May, June and the last week of August. More in what auditors reject.

How Palau handles this

Palau keeps the Ladder file as structured data. Reef stores your footprint data once, and 3.1, 4.0 and ESRS E1 are all served from it. Vault manages the evidence and links each document to the data point it belongs to, so you can see which support moves across to a 4.0 requirement and which requirement is still empty. The organisational structure module records which entities sit under which certificate, which matters for groups where the organisational boundary runs across several entities. Background: our CO₂ Performance Ladder page.

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