It's a Swiss legal entitlement. Even one day of sickness absence can extend the notice period by one month. It's often seen as, and often used as taking advantage but thems the rules!

Why not? What stops it being indefinite, within the law?

Nope there’s a cap depending on tenure.

OP the clause in the contract is illegal.
Garden leave has no relevance.
If you’re sick during notice period (if you’ve been terminated, not if you have resigned yoursef), the notice period extends by the # of days you’re off sick, but as employments can only be terminated by the end of the month, it extends by a month. So you’re understanding is correct.

Of course not, the first extension-month needs to be filled first. The employer will have requested a check by a doc of their choice long before that.

This is neither taking the piss, cheating nor fraudulent just because you don't like it. It's a legal entitlement.

Even if you are sick for one day and get a doctors certificate to say you, you are following the law.

Jep even if you have a headache and stay in bed for a day, if a doctor is willing to give you a certificate for that, the notice period is extended (again only if you've been terminated and assuming you were on a permanent/open-ended contract).

Now whether that is morally right or not is a separate question, but legally it's fine.

You don't need legal insurance nor does RAV step in (RAV has no legal power here). Send your doctor's certificate with a letter about extended notice period as per the law to your former employer and see what happens.

If that first attempt fails - and it probably will - have a lawyer follow up, fairly sure they will back off immediately as it literally doesn't get any more clear-cut than this case. You have law 100% on your side, they can try to bypass this contractually as much as they want, but stand zero chance. Again, certain conditions apply, but we've already outlined those.

Usually. I believe it's not always the case. I know many people with a 30 calendar day notice period but it always raises my eyebrows.

Default is end of the month, but this particular article/law in OR can be changed. Upon mutual agreement and provided the same rules apply for both parties, it's ok to agree on another day, albeit very unusual in this country.

Doesn't seem to be the case with OP though.

Samaire 13 thank you for this information. I confirm this is not my case.

Samaire 13 thank you, it helps a lot!

Today Only, I don't "just" want one extra months' salary. After I had been sick, I was told about that rule and I just wanted to know more about it. If this is law, I don't see why I should not use it. Anyway if I find a new job sooner than the end of the notice period (which I hope), I won't get it. It's just a sort of extra insurance for me in case things get longer.

Guys you are amazing, thanks for all these responses

That's a very good point. I have been there for 18 months and it is my first job in Switzerland, so yes, the reference letter matters a lot.
I haven't received the reference letter yet and I hope they won't take my sick leave as a bad signal. I had to send them the doctor's paper and I could not wait until I got the letter... too bad.

You will need your old employer's Ok for that. And of course if it is agreed that the old contract ends earlier, the salary payments stop earlier as well.