Force of law, or reference only: reading the CBAM notices before you price a client's imports

Same page, different legal weight

Open HMRC's publication for the Carbon Border Adjustment Mechanism and you are looking at material of two different kinds sitting under a single heading. Some of it is notice text made under powers in the Finance Act that introduced CBAM, and HMRC marks that text as carrying the force of law. The rest is a reference document whose job is to explain, illustrate and cross-refer.

A founder will not see the seam. The page reads as one continuous official source, published by the authority that will later assess and collect. That impression is understandable and it is wrong in a way that matters the moment a position is challenged.

The practical test is simple: ask of any sentence you intend to rely on whether it creates a duty, or describes one that exists elsewhere. Explanatory text can be persuasive about HMRC's view. It cannot be the authority for a duty it only narrates.

What "force of law" actually does here

The CBAM legislation does not spell out every operational detail in the Act. It leaves specified matters to be set out in a notice published by HMRC, and where that is so, the notice text does legal work: it fixes the content of an obligation the Act has already authorised someone to fix.

So the chain runs in a direction worth saying out loud. The Act creates the liability and the power. The notice, acting under that power, supplies the detail the Act told it to supply. The reference document then stands beside both and tells you what they mean.

This is why a notice can be short and still decisive, and why a long reference document can be helpful and still carry no weight. Length is not authority. The authorising provision is.

The source walk: tracing one obligation to the sentence that creates it

A source walk is what we do at delivery: open a key number with the client and show where it lives in the law. Try it on CBAM before you quote a client a landed cost.

Pick the obligation. Say it is the way an importer must evidence the embodied emissions of a consignment, or the basis on which a default figure applies when actual data is not available. Now find, in the Act, the provision that says this matter is to be specified in a notice. That provision is the hinge. Without it, no notice paragraph can bind anyone on the point.

Next, find the paragraph of the notice itself that answers the question, and check that it is inside the part of the publication HMRC identifies as having the force of law. Record the paragraph reference, not the page. Page structures move between revisions; paragraph references survive longer and are what a review will ask you for.

Only then read the reference document. Use it to confirm you have understood the notice, to see the worked illustration, and to notice where HMRC's explanation is broader or narrower than the operative words. Where they diverge, the notice governs and the divergence is itself worth a file note.

If the walk ends in the reference document with nothing behind it, you have not found a rule. You have found a view. Both are useful. They are not interchangeable in a dispute.

Absence is information: what the notices leave to later publication

Read the CBAM material for what it does not yet settle and you learn as much as from what it does. Some matters are stated to be dealt with in a notice to be published, or in a later revision. Others are described in the reference document in terms that signal guidance rather than specification.

That absence is not a gap in your research. It is a dated fact about the state of the law, and it belongs in your advice in those words. "HMRC has not yet published the notice specifying this; here is the range of outcomes it could fix, and here is the trigger that will tell us" is a defensible sentence. "HMRC requires" is not, if no notice says so.

Advisers get into trouble by smoothing. A founder asks what the number is, and the honest answer is sometimes that the number is not yet fixed, with a stated date of checking and a stated place to watch. Absence is information.

Why this lands on pricing, not just compliance

Founder-led importers price forward. They quote a customer, sign a supply contract, commit to a landed cost, and only later meet the assessment. CBAM detail that is specified by notice therefore sits inside commercial promises made before the notice is read.

Two distinct risks follow. Where a notice already specifies the point, a quote built on the explanatory gloss can be wrong in the direction of the client's margin. Where the notice is still to come, a quote built on an assumption will need a contractual mechanism to move, rather than a hope that the eventual specification is kind.

Both risks are addressable by the same discipline: for every emissions, evidence or valuation input that moves the price, write down whether it comes from the Act, from operative notice text, or from explanation — and date it. That column is what turns a spreadsheet into a position you can defend.

What we put on The Floor

We publish our own numbers quarterly, including in the quarter the number is bad, and we show both ends of the range rather than the end that flatters us. The published range is "From 24% to 98%". The published counts are "4,790+" (as of September 2026) and "870+" (as of September 2026).

We are not going to restate those figures here as if they measured CBAM specifically. They do not. Treating a published number as evidence for something it was never about is the same error as citing a reference document for a duty it only describes, and we would rather name the limit than borrow the credibility.

What we can say about CBAM is narrower and dated: the material on HMRC's publication page separates operative notice text from the reference document, and parts of the detail are left to later publication. That is the state of the source as we read it, and it is the state we will correct in public when it changes.

What we don't know

We do not know which of the matters left to later notices will be specified in terms that match the current explanatory treatment. Where HMRC's reference document illustrates an approach, that illustration may survive into operative text, or it may not, and we have no basis to tell a client which.

We do not know how revisions will be versioned on the page, which means a position you take today may become hard to reconstruct unless you keep the paragraph reference and the date you read it. Keep both.

The judgment here stays human. A source walk tells you which sentence creates the obligation and which only explains it; it does not tell you what to advise. The professional decides and signs. Our interest is that days of source-hunting become a focused review, with the authority for each number open on the screen when the client asks why.