Hello,
How may I declare to the authorities that I am planing to leave Switzerland starting from some period for more than 6 months, before my B permit expires (this is for instance necessary in order to cancel the insurance fees)? What documents should I provide?
Thanks!

I suggest you speak to your Gemeinde ( Einwohnerkontrolledienst ) - they might suggest you do a de-registration ( Abmeldung ), which is performed within minutes.

For Stadt Zürich, here is the link in DE.

In EN:

Source from another Gemeinde

Thanks! I thought I should contact the Kreisbuero regarding d-registration...

Yes, you will need to de-register. I think jrspet believed that you wanted to put your B permit on hold...

Yes. Kreisbüro is an expression unique to the town of Zurich. Elsewhere your town hall (Gemeindehaus) will be the place...

To my knowledge, putting it on hold ( judging from your other thread ) applies only to C permit holders ( Abwesenheitsbewilligung - Niederlassungsbewilligung aka permanent residence cf B temporary residence ).

There is a form you fill out when leaving. On the D2 form (formulaire de depart I think) for leaving Geneva, there is an option to note if it is a termporary or permanent move. With this form you can get a certified letter (25 chf fee) that you are leaving, and you can give this to the insurance company and others.

In the city of Zurich, you need to go to the Stadthaus, not the Kreisbüro. Then you can start the fun of paying taxes, going to get cash, etc, etc.

Yes in Zurich you need to go to the Stadthaus. Only after you've paid the taxes they will give you the confirmation that you are moving abroad (which you will need to cancel health insurance, mobile phone contract etc).