Re: some questions about filling announcement of depart (form D)
Geneva is very special when it concerns administration. I would visit the tax office and ask for the certificate.
They will ask you to complete the tax return form for the year 2015. You work for 2 hours, then give them the completed form, and they say come back next month as they need time to evaluate the information. You tell them you are leaving this week, and they then stamp your leaving form.
Good luck, you'll need it!