In short
- The start date is 1 December 2010. Nothing about ProRail's CO2 criterion begins in 2027.
- On 1 January 2027 ProRail intends to switch to Handboek 4.0 for newly published TenderNed procurements, with a provisional 4, 7 and 10 percent staffel.
- The date that governs a given bid is the date that procurement was published, and its documents are decisive over anything published on ProRail's website.
The next date on ProRail's CO2 calendar is 1 January 2027, and it changes the handbook version rather than starting anything. ProRail has applied the CO2-Prestatieladder as an award criterion since 1 December 2010, using the tendering method SKAO recommends. From 1 January 2027 it intends to use Handboek 4.0 in all newly published TenderNed procurements where the Ladder is an award criterion, with a provisional weighting of 4, 7 and 10 percent by trede. Any source describing 2027 as the year ProRail starts scoring carbon is fifteen years late.
Which dates exist at all?
Fewer than you would expect. Two are still ahead, and only one of those is ProRail's own.
| Date | Status | What it is | What has to be true |
|---|---|---|---|
| 1 December 2010 | Spent | ProRail begins applying the CO2-Prestatieladder in procurement, using the method SKAO recommends to all buyers | Nothing. It is the answer to "when did this start" |
| 4 June 2026 | Spent | SKAO publishes ProRail's announcement of the switch to version 4.0. The date the intention became public | Nothing takes effect. It dates the announcement |
| 29 June 2026 | Spent | ProRail webinar with SKAO explaining the change, registration having closed on 23 June 2026 | Not a milestone. Noted only because it dates the announcement |
| 1 January 2027 | Ahead | ProRail intends to require version 4.0 in newly published TenderNed procurements where the Ladder is an award criterion. Provisional staffel of 4, 7 and 10 percent by trede | Your bid team knows which version each live opportunity runs on |
| 14 January 2027 | Ahead | Scheme-level date, set by SKAO rather than ProRail: the last day a 3.1 audit may be performed | Your own migration is booked. ProRail flags that certificates from those audits stay valid until the next annual audit or the end of their term |
That is the whole calendar. There is no separate ProRail deadline for holding a certificate, because ProRail does not require one to bid.
Why does a 2010 date belong on a deadlines page?
Because the most common mistake about ProRail is a date error that reads as a strategy error.
If you believe the criterion arrives in 2027, you conclude that carbon performance is irrelevant to ProRail work today and that there is a year to prepare. Both conclusions are wrong. ProRail states that the certificate has given an advantage in virtually all of its tenders, as a fictitious discount on the bid price that can run up to 10 percent, for the entire period since 1 December 2010. Bidders have been losing and winning on this criterion for fifteen years.
The correction changes the question from "should we get ready for 2027" to "what have we been leaving on the table since we started bidding here".
What actually happens on 1 January 2027?
The version changes and the staffel is redrawn, because Handboek 4.0 has three treden where version 3.1 had five niveaus.
ProRail's stated provisional weighting under 4.0 is a fictitious reduction of the bid sum of 4 percent for CO2-ambitieniveau trede 1, 7 percent for trede 2 and 10 percent for trede 3. It confirms that, as now, bidders will not have to produce a valid certificate at bid time.
Everything else stays where it is. The Ladder still appears as a project-related subcriterion, the declared ambition level still becomes a contract condition on award, and ProRail still checks realisation during execution with proof by project-specific evidence or a matching CO2-bewust certificate.
Why is ProRail's date two weeks before the scheme's?
Because they are answering different questions, and the gap is a small but real planning trap.
1 January 2027 is ProRail's own choice about which handbook its tender documents refer to. 14 January 2027 is SKAO's deadline for the certification side: the last day an audit against Handboek 3.1 may be performed at all. So for a fortnight there is a window in which ProRail is publishing new procurements under 4.0 while 3.1 audits are still legally being carried out somewhere in the market.
That matters only if you were planning to squeeze in one last 3.1 audit and expected it to serve a new ProRail bid. It will not serve a procurement published from 1 January. It may still serve procurements published before that date, which keep the existing arrangement.
Which date governs a given bid?
The date that procurement was published, not the date you submit and not today's date.
For tenders started before 1 January 2027 where the Ladder is an award criterion, ProRail's existing arrangement continues: version 3.1 is the basis and a version 4.0 certificate is also accepted as proof, under ProRail's own equivalence. It reads trede 1 as niveaus 1, 2 and 3, and treden 2 and 3 as niveaus 4 and 5, and applies the same equivalence to running contracts. That last point exists precisely because a contractor can end up holding only a 4.0 certificate part way through a ProRail contract once 3.1 audits stop.
For anything published from 1 January 2027, the intention is 4.0. And in every case ProRail states that its tender documents on TenderNed, not its website, are decisive for the exact arrangement that applies.
What has to be true in your own calendar?
Three entries, and none of them is 1 January.
Your migration to Handboek 4.0. Driven by the scheme rather than by ProRail, and pinned to your own audit cycle rather than to 14 January 2027 itself. Book the conversation with your certifying body well ahead of it.
Your declared ambition levels on live contracts. Every level you declared is a contract condition that ProRail checks during execution. A version switch does not reset those.
Your bid calendar split by publication date. For a period you will be running some bids on niveaus and some on treden, and the mapping between them is ProRail's rather than the scheme's.
What is not fixed by any of these dates?
The percentages. This deserves saying loudly because it is the part most often quoted as settled.
ProRail's language is conditional throughout: it says it wants to use Handboek 4.0 from that date, describes the 4, 7 and 10 percent figures as voorlopig, meaning provisional, and SKAO reports the weighting as voorgenomen, meaning intended. ProRail adds explicitly that a different weighting can apply to some tenders. There is also no published per-level staffel for the five niveaus in use today, only the ceiling of up to 10 percent, so you cannot build a clean comparison of what a level is worth before and after.
The useful figure to plan on is not any of the three headline percentages. It is the gap between adjacent treden, which is 3 percentage points, because that is what moving up buys you on the ranking of a bid.
Where does the work behind these dates sit?
In an organisational carbon inventory somebody else has to be able to follow. Scope 1 and 2 for trede 1, quantified scope 3 and a klimaattransitieplan, a climate transition plan, for trede 2, and a quantified route to zero emissions by 2050 for trede 3.
The Hedgehog platform names the CO2-Prestatieladder among its reporting outputs, holds over 20,000 spend-based and activity-based factors that you can supplement with your own supplier-specific data, and reports 5,000+ users on its platform page. The limitation to test well before an audit date rather than against one: a mid-market reviewer on G2 in July 2026 rated it 4 out of 5 and reported that the conversion factors and distance calculations applied to an input are not visible in the interface, so a full trace from entry back to source is not always possible without asking. On an instrument where a certifying body follows numbers backwards, find that out on a quiet week.
If the trede decision rather than the tooling is what is holding you up, that is carbon footprint consulting work. If you are picking a tool for the first time, our guide to choosing the right carbon accounting software covers what to ask, and our introduction to the CO2-Prestatieladder for SMEs covers the scheme.
Sources: ProRail supplier page on the CO2-Prestatieladder, SKAO news item of 4 June 2026 reporting ProRail's announcement, Hedgehog platform, Hedgehog on G2. Verified 28 August 2026.
Facts on this page were last verified on 2026-09-17.
