The difference in nature
In public contracts, the procedure cannot depart from the rules. The obligations are statutory, they bind the contracting authority, and disregarding them affects the validity of the procedure.
In private contracts, the procedure is more flexible but its structure remains broadly the same. The obligations are no longer statutory; they are contractual.
This distinction has a direct consequence: in private work, what is not written in the tender documents is not owed.
A private client need not give reasons for its choice, nor treat candidates equally, save where it has undertaken to do so in the documents it issued.
Conversely, it enjoys no default framework, which makes the quality of its documents all the more decisive.
| Element | Public contract | Private contract |
|---|---|---|
| Procedural framework | Set by regulation | Set by the parties |
| Thresholds | Determine the procedure | Not applicable |
| Advertising | Compulsory above the threshold | Free |
| Standardised documents | Commonly used | Used by reference |
The thresholds applying to public work
They determine the procedure and are worth knowing, including by those who work only in the private sector. The thresholds govern the applicable regime.
The general rule is the open procedure.
Below a first threshold, the negotiated procedure or the restricted procedure without notice is available without further justification. The official sources set this threshold at seventy-nine thousand euros excluding tax.
Between that and a second threshold, those procedures remain available provided at least three candidates are invited, where enough suitable candidates exist.
Above a third threshold, the restricted procedure with notice becomes available without justification, the contracting authority retaining the choice with the open procedure. A separate and markedly higher threshold applies where the works are carried out by a general contractor.
How the thresholds are updated
A technical point that explains divergence between sources. The thresholds are revised periodically.
The statutory thresholds are expressed against an old reference index, not in current euros.
They are updated annually, giving values far above the nominal amounts appearing in the texts.
A nominal threshold of one hundred and twenty-five thousand euros thus corresponds to an updated value several times that amount.
Practical consequence: never reproduce a threshold figure without checking its year of update.
This mechanism is not confined to public procurement. It recurs in other Luxembourg schemes, notably tax ones, covered in the guide on housing tax and support.
What remains common to both regimes
Four elements, independent of the regime. They belong in the documents whether the contract is public or private.
The structure of the specification, in contractual and technical clauses, general and particular, with a schedule.
The requirement of a clear and detailed description, without which no comparison is possible.
The principle that the documents issued bind, annexes included.
The need for a common basis for every contractor invited, covered in the article on what makes bids comparable.
The error of transposition
It works in both directions.
Applying public rules to private work imposes needless constraints, notably of publicity and reasons.
Applying private flexibility to public work exposes the procedure to invalidity.
The second error is the graver, but the first is the commoner, notably among those used to public procurement.
A third situation exists: a private client may choose to impose rules inspired by the public regime, which is lawful but then binds it contractually.
What this means for a professional
Four rules.
Identify the regime before assembling the package, the nature of the obligations depending on it.
In private work, write what you want applied, no default framework supplementing the documents.
Never reproduce a threshold without its year of update, nominal amounts being misleading.
Do not transpose the rules of one regime to the other, in either direction.
This article reflects the rules at the date of checking and serves professional orientation. It does not constitute legal advice.