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In short: A cost estimate (the Swiss Code of Obligations calls it an "approximate estimate") is a ballpark, not a fixed price. If it is exceeded "disproportionately" through no fault of the client, the client may withdraw from the contract (Art. 375 CO). The law names no percentage; in practice, around 10% is the usual guide. A fixed price, on the other hand, binds you even if the job took more work than planned (Art. 373 CO). So always state whether your price is an estimate, a cost ceiling or a fixed price.
You want to name a price the client can simply accept? That is a binding quote: use the Swiss quote template.
Three clauses to copy
Disputes are rarely about the amount and almost always about unclear wording. Take the clause that matches what you really promise.
1. Non-binding estimate
This cost estimate is non-binding.
Prices are based on the effort known today and may vary depending on
the material and time actually required. If additional costs become apparent,
we will inform you before carrying out the work.
2. Estimate with a cost ceiling
The following estimate is based on the current state of the project.
The total of CHF 3'500.00 will not be exceeded without your prior approval.
3. Fixed price
Fixed price for the services described below: CHF 2'800.00 excl. VAT.
This price is valid until [DD.MM.YYYY].
With the third clause your document is no longer an estimate but a binding quote, even if it says "cost estimate" at the top.
What to leave out:
- "approx." in front of the total without saying what the estimate is based on
- no validity date
- no word on VAT (included or excluded?)
- catch-all items such as "miscellaneous work"
- no rule for additional work
When is a cost estimate binding?
For contracts for work and services (trades, construction, repairs and any other work you deliver), the Code of Obligations distinguishes three cases:
| What you wrote | What the law says | What it means for you |
|---|---|---|
| Fixed price | You must complete the work for that sum and may not ask for more, even if it took more labour or higher expenses than foreseen (Art. 373 para. 1 CO). | The risk is yours. In return, the client pays the full price even if you had less work (para. 3). |
| No price or only an approximate price | The price is set by the value of the work and your expenses (Art. 374 CO). | You bill the time and materials actually used. Your estimate remains the yardstick your client relies on. |
| Approximate estimate exceeded "disproportionately" | If the client is not at fault, they may withdraw from the contract during or after the work (Art. 375 para. 1 CO). For buildings on their land, they can ask for an appropriate price reduction instead (para. 2). | Report additional costs as soon as you see them coming, and get them confirmed in writing before you continue. |
And the 10 percent rule? It is not in the law. Art. 375 CO says "disproportionately" and names no figure. In practice, around 10% is the usual guide for what a client still has to accept. That is neither an entitlement for you nor a hard limit: it depends on what you wrote and on the case. Three habits protect you:
- Write down your assumptions. Access to the site, material prices on the day of the estimate, what is not included.
- Report before, not after. If an item gets out of hand: an email with the new amount and the reason.
- Get it confirmed. A written reply from the client is worth more than a yes on the phone.
If the client changes the job along the way, the extra cost is theirs: record the request and its price in an addendum or an email.
What the template contains
The download is the English Swiss quote template, one A4 page as Word or PDF. To use it as a cost estimate, change the title to "Cost estimate (non-binding)", write "approx." in front of the quantities and the total, and replace the note above the signature with clause 1 or 2 from above.
- Sender and recipient, with your UID if you are registered for VAT
- Title, number, date and validity (30 days)
- Line items with quantity, unit, unit price and total
- Subtotal, VAT 8.1% and total; if you are not registered for VAT, delete the VAT line
- Terms: payment terms, timing, and what is not included
- Acceptance: place, date and the client's signature
Your client reads German? The German Kostenvoranschlag template already has the non-binding clause, an assumptions block and an optional cost ceiling.
