The principle and the condition
Three basic points.
Without a revision clause, contract prices remain unchanged throughout execution.
On a short project this is acceptable. On a long one it transfers to the contractor the risk of cost movement, which it then builds into its initial price.
A firm price is therefore not necessarily cheaper: it incorporates a risk allowance that revision would render unnecessary.
The choice between firm and revisable prices is an economic trade-off, not a formality.
| Element of the clause | What it fixes | Effect if missing |
|---|---|---|
| Formula | The method of calculation | Clause inoperable |
| Indices used | The series applied | Calculation open to challenge |
| Base date | The starting point | Wrong result |
| Frequency | The rhythm of revision | Argument at every valuation |
| Scope | The items subject to revision | Dispute over the base |
The reference index
This is the technical heart of the clause. It concerns the formula used and its indices.
Revision presupposes a reference index, whose movement measures that of costs.
In Luxembourg the construction price index is compiled by the national statistics institute, with summary indices by trade.
Its frequency is half-yearly, with surveys in April and October, published with a lag of several months.
That frequency has an important practical consequence: a contract signed between two publications has no contemporaneous index, and the clause must specify which applies.
How this index works is covered in more detail in the guide on construction costs.
The exceptional scheme in force
A development to know, with its cut-off date. It concerns the indices used in revision formulas.
A ministerial communication of 1 July 2026 opened a scheme for price revision in respect of extraordinary increases in the prices of materials and energy.
It allows contractors performing public contracts to seek compensation for extraordinary additional costs.
It applies immediately to contracts in progress and to contracts whose tenders are opened up to and including 31 December 2026.
The government also invites contracting authorities to show flexibility where supply difficulties or delays in execution are linked to the economic situation, extensions of time or contractual adaptations being available where circumstances justify.
The contractors concerned are invited to document cost increases and to inform their contracting authority without delay.
A calculation method and explanatory note have been made available by the competent sector body, with a tool updated monthly.
This scheme concerns public contracts. Extending it to a private contract can only result from agreement between the parties.
What a clause must specify
Five elements, without which the clause is inoperable. They make up a workable revision formula.
The index adopted, unambiguously identified.
The revision formula, and notably the share of the price subject to revision.
The base date, serving as the reference.
The frequency of application, and the treatment of intervening periods.
The position of additional works, revisable or not on the same terms.
The fifth point is the most often omitted, and it produces discussions at the final account.
What revision does not cover
Two limits.
It does not cover increases specific to one contractor, arising from its organisation or procurement.
It does not cover changes of programme, which fall under additional works.
A revision clause is therefore not a general protection against cost increases, but an adjustment measured by an index.
What this means for a professional
Four rules.
Treat the choice between firm and revisable prices as an economic trade-off, referred to the length of the project.
Specify the five elements of the clause, omitting none.
Check the state of exceptional schemes at the time of tender, the one in force being time-limited.
Document the increases where an exceptional scheme is invoked, the claim needing to be evidenced.
This article reflects the state of the schemes at the date of checking and serves professional orientation. It does not constitute legal advice.