29 August 2026
Whether a variation can be enforced is decided not by the amount of extra work, but by which of the three pricing forms of the Code of Obligations was agreed. At a fixed price the client owes not a centime more — not even if the contractor took twice as long.
The flat is finished, the Rapport — the signed record of the work done on site — has been signed, and the final invoice is 4'800 francs above the quote, because the existing installation was not what had been assumed and two extra days of work were needed. The customer pays the quoted amount and strikes out the rest. Who is in the right turns on a question that was answered long before the extra work: which pricing form is in the contract?
The Swiss Code of Obligations (OR) knows three, and they lead to three different answers. Most disputes arise because the two sides are working from different forms.
If the price was fixed exactly in advance, the contractor is obliged to complete the work for that sum, and may not demand any increase, even if the work involved more labour or greater expense than anticipated (Art. 373 para. 1 OR).
That is the hard rule, and the most underestimated one in the whole law of contracts for work. "We needed two days longer" is not a claim under a fixed price, but a costing error — and it stays with the contractor. The same logic works the other way in the contractor's favour: the client must pay the full price even if completing the work took less labour than anticipated (Art. 373 para. 3 OR).
Art. 373 para. 2 OR opens a door, but only a crack. What it requires are extraordinary circumstances that
If these are met, the court may, at its discretion, allow an increase in the price or the termination of the contract. Three things stand there that are regularly read past in practice: a court decides, not the contractor; it is discretion, not an entitlement; and "excessively difficult" is more than "turned out more expensive". An existing installation that looks different from what was expected is not an extraordinary circumstance on a renovation — it is the normal risk of the job.
The cost estimate is the most dangerous of the three forms, and in the direction nobody expects. If an approximate estimate agreed with the contractor is exceeded disproportionately without any act of the client, the client has the right to withdraw from the contract — both during and after the execution of the work (Art. 375 para. 1 OR).
After the execution. The work is done, and the contract falls away all the same.
For buildings on the client's own land a milder variant applies: the client may demand an appropriate reduction of the price or — if the building is not yet complete — take the continuation of the work away from the contractor against fair compensation for the work already done (Art. 375 para. 2 OR). For an electrical contractor, who almost always works on someone else's land, it is usually this second variant that applies, and it comes down to a reduction.
"Disproportionately" is not defined, and that is not a gap but a matter of discretion in the individual case. Anyone who names an estimate therefore owes one thing above all: to say in good time that it will not hold.
If the price was not fixed in advance at all, or only approximately, it is set according to the value of the work and the expenses of the contractor (Art. 374 OR).
That is the legal basis of Regie — work outside the quote, billed at rate — and it is the friendliest form for the contractor: the price follows the actual expenditure. But it is also the one that demands the most proof: "the value of the work and the expenses" must be shown in a dispute, hour by hour and item by item. A Regie order without properly kept Rapports is an order whose price cannot be quantified in court.
A variation is enforceable if it reflects a change in scope — additional work that was ordered — not if it corrects, after the fact, a costing error on the agreed work. The dividing line does not run along the size of the amount, but along the question whether the client ordered something different, or something more.
In practice this means:
The client has to pay on delivery of the work (Art. 372 para. 1 OR) — not thirty days after the invoice date, unless something else was agreed. If the work is to be delivered in parts and the price has been set per part, each part is to be paid for on its delivery (Art. 372 para. 2 OR). That is the legal basis for Akonto payments — payments on account — by construction stage, and it applies only if the division is in the contract. Details, and the exception when the customer becomes insolvent, are in the article "Asking for an Akonto as an electrical contractor".
Anyone wanting to keep the inspection duties around acceptance apart will find them in the article "Initial verification, final inspection, acceptance inspection". Which inspection period applies to an installation is shown by the inspection period calculator. What matters when choosing software for Rapports and quotes is covered in the article "Trade software for electrical contractors: what matters for Rapports, quotes and costing". What applies when the final invoice stays unpaid — default, default interest, Skonto and a contractual retention — is covered in the article "Unpaid invoice: default, default interest, Skonto and retention". When an Akonto can be demanded and when it cannot is shown in the article "Asking for an Akonto as an electrical contractor".
Sources: Swiss Code of Obligations (OR, SR 220), Art. 372, 373, 374 and 375, fedlex.admin.ch, version retrieved on 28 August 2026. Where the articles are quoted, they are rendered from the official text. This article does not replace legal advice: whether a particular circumstance is "extraordinary" within the meaning of Art. 373 para. 2 OR, or an overrun "disproportionate" within the meaning of Art. 375 para. 1 OR, is decided in a dispute by the court in the individual case.
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