What a bill is, legally
Belgian public procurement rules define the summary bill of quantities as the document, specific to works contracts, that divides the works into distinct items and states, for each, the quantity or the manner in which its price is to be determined. The definition is regulatory rather than customary, which gives it contractual force.
Three elements deserve noting.
Division is the primary function. It determines what contractors will price, and it is not neutral.
The quantity is not always given. The alternative of a method of determination opens the way to global prices and provisional items.
The document belongs to the contract. It is not an internal working paper but a contractual element binding on the parties.
A bill is therefore not an estimate. An estimate assesses a probable cost; a bill describes a scope and quantities. One can prepare a bill without knowing a single price.
These notions are developed in the article on the bill and its contractual function. That article is best read before the detailed ones.
Three frameworks, no unification
| Framework | Scope | Nature |
|---|---|---|
| CCTB | Wallonia and the French Community | reference by citation |
| Flemish building framework | Flanders, the most used basis | full transcription of articles |
| Federal framework | Buildings Agency | neither standard nor reference specification |
Private coding systems are added, distributed by software vendors and maintained by practices. Their contractual status depends on the contract that invokes them.
The structural difference: citation or transcription
This is the point everyday vocabulary conceals, and it is not cosmetic. The Belgian frameworks do not rest on the same updating mechanism.
The CCTB is a citation document. The particular specification does not copy the prescriptions: it cites the framework and states only the clarifications, additions and derogations specific to the contract.
The Flemish framework works the other way. It is not a citation document: the relevant articles are transcribed in full into the particular specification, starting from the most recent version. The document becomes self-contained.
This is not a matter of presentation but a transfer of responsibility. Under transcription, updating falls to the author of the particular specification, permanently, the publishing body expressly disclaiming liability for the texts transcribed.
The two methods therefore expose users to different errors: identifying the version on one side, invisibly obsolete text on the other. The check to be carried out therefore differs with the framework.
The federal document is not the CCTB's counterpart
A widespread confusion deserves clearing. The federal body states itself that its technical document is neither a standard specification nor a reference specification: citation is excluded, the texts must be transcribed.
It further states that only the structural chapters are kept current, the others no longer since 2008. Transcribing a non-structural chapter today therefore means transcribing a text frozen for more than fifteen years.
What the absence of unification costs
Three effects, regularly reported.
Exchanging bills is laborious, two different coding systems not aligning automatically.
Comparing tenders becomes harder where contractors respond on different bases.
The move to BIM suffers, for want of a common system of attachment.
This is not an outsider's opinion: the Belgian industry has itself called for years for a single working methodology, covering texts, bills, drawings and digital classification. The calls for harmonisation come from the professional federations themselves.
These frameworks are covered in the branch on the three frameworks. They are compared there item by item.
Its exact scope
The CCTB carries authority for public contracts and subsidised works of the public services of Wallonia and of the French Community. Its use outside that scope rests on a contractual choice.
Two clarifications are needed. The French Community is a community, distinct from the Brussels Region. And in the Brussels-Capital Region the CCTB has no regulatory status: it is used there as a de facto reference, with nothing imposing it.
Beyond that, its use may be imposed contractually by a client, a designer or a subsidising authority. The practical question is therefore not "is the CCTB mandatory" but "does this contract impose it".
Its structure
The framework has ten technical parts, numbered zero to nine, an administrative volume carrying the legal and contractual clauses, and annexes. That structure governs how an element is searched for.
The technical parts approximately follow the sequence of construction operations, which makes searching intuitive for a construction professional. Searching by sequence is therefore faster than searching by keyword.
One limit is worth knowing: that structure is a good drafting plan, but it is not a construction programme. Continuous works such as site set-up, protection and waste management are attached to a single part by convention.
Its annual update
This is the characteristic with the heaviest consequences, and it is specific to the CCTB. It stems from the annual update of the framework.
The version in force on 8 August 2026 is 01.13, published on 17 March 2026, preceded by 01.12 of 18 February 2025. The next is expected early in 2027.
The transition rule is nuanced. For a contract not yet published, the new version renders the earlier one obsolete. For a particular specification being drafted, the same version is kept until the end of the project, absent a significant legal or safety change.
Hence a rule running through this whole guide: cite the version of the framework, with its date, in the particular specification as in the bill.
These points are covered in the branch the CCTB in practice and in the article on the annual update. The drafting method is set out there step by step.
Reading a line of a bill
A line looks simple: a heading, a unit, a quantity, a rate. Each of those columns commits differently.
The anatomy of an item
An element has an index, its position in the classification, a title, a short designation, and a description, the detailed content. Those three components are cited together and not separated.
The title does not make the content. It is the description that states what the work comprises. A bill read without its descriptions is a list of headings, not a scope, and that error is all the more frequent because bills often circulate alone, in a spreadsheet.
The four ways of determining price
Provisional quantity: firm rate, payment on quantities actually executed.
Lump-sum quantity: fixed quantity, no adjustment.
Global price: item priced as a whole, without quantity.
Provisional item: present without an amount, which means neither free nor excluded.
The distinction between provisional and lump-sum determines who bears quantity risk, and it carries the heaviest consequences.
The unit carries a measurement rule
A unit is not a label. Two bills using the same square metre can give different quantities if deduction rules for openings differ.
The costliest errors are known: confusing developed and projected area on roofs, linear metres applied to a varying section, a unit by number where an assembly is expected. They are prevented by a systematic check of units and conventions.
These notions are developed in the branch what a bill is. The measurement conventions are set out there item by item.
The rule of order
The bill derives from the selection of prescriptions, never the reverse. That is the step most often reversed, by starting from a bill borrowed from an earlier project, and it is the principal source of discrepancy.
A particular specification does three things, and only three: it clarifies a choice left open, it adds work not provided for, it derogates from an applicable provision. What it should not do is copy: a duplicate becomes a divergence at the next version.
The four forms of discrepancy
Item without prescription, prescription without item, divergence of content, divergence of unit. The second is the costliest: work described but not priced will be carried out and invoiced without competition.
The cross-check of indexes catches most of them: comparing the list of indexes cited in the bill with that of the elements selected, in both directions. That check takes minutes and prevents weeks of argument.
What BIM changes and does not change
A model produces quantities. It does not produce a bill.
The reason is structural: Belgian specification frameworks are enumerative, each element occupying a single position in a hierarchy, whereas digital classification systems are predominantly faceted. Moving between them is design work, not conversion.
The choice of division, the measurement rules, the unmodelled works and the classification as provisional or lump-sum remain human decisions. That part, not derivable from the model, is precisely the one producing most disputes.
These points are covered in the branch drafting without inconsistency. The method is described there for spreadsheets as well as integrated tools.
The framework
Three texts structure the matter: the Act of 17 June 2016 for the general framework, the royal decree of 18 April 2017 for award, the royal decree of 14 January 2013 for execution. They are amended regularly, and the applicable version is the one in force at the launch of the contract.
Verification and rectification
The contracting authority submits tenders to a verification of prices, an obligation and not an option. It first seeks the tenderer's real intention, questions them only if that search fails, rectifies according to its own findings absent an acceptable clarification, and may ultimately decide that the unit rates apply or reject the tender as irregular.
Its liability is not engaged where it fails to detect an error. There is therefore no safety net for the careless tenderer.
Silence does not pay
Under a provisional quantity, speculating on an understated quantity gains nothing, since the excess will be due at the rate offered. On an omitted item, the contractor who said nothing then negotiates from a weakened position.
Execution
The bill then changes function and becomes an instrument of payment. Two rules follow.
What is about to be covered is recorded before it is, jointly and in writing.
A variation is not additional work. The first is the normal working of the contract, at the agreed rate. The second is a change, negotiated without competition.
Under provisional quantities, the gap between the contract sum and the final account is normal, not an overrun. The final account reflects the quantities actually executed.
The time limits that forfeit a right
A contractor seeking a revision or damages must submit a quantified written justification at the latest ninety days after notification of the certificate of provisional acceptance. Beyond that period the right is lost, however strong the case.
These mechanisms are covered in the branch public contracts. The tenderer's duty to check the quantities is explained there.
The method, in summary
Six rules, applicable whatever the framework. They concern citing indexes, the units and the cross-checks.
1. Identify the framework and its version before any other reading.
2. Never price without the descriptions. The heading does not define the scope.
3. Derive the bill from the selection, not the reverse.
4. Check in both directions, items to prescriptions and prescriptions to items.
5. Cite the version in the documents, with its date.
6. Report what is spotted, within the time limits and in writing.
The detailed checking method sits in the article on checking a bill received, and the method for reconciling regions in that on comparing a Walloon and a Flemish bill. It is applied before tender submission rather than after.
This guide reflects the position of the frameworks, the rules and professional practice at the date of checking and serves as orientation. It does not constitute legal advice and does not replace consulting the official sources.