in theory you pay taxes in the commune where u are resident at 12/31.

You did not read properly the calculation mechanism for the canton of Zurich (I assume it is similar for other cantons): There are two factors determining the tax at source:
1.Your tax "Tarif" - depending on your marital status and number of kids. This is being reported by the place where you live (they have the data).
2. The tarif and your salary is then applied to the tax tables ("Steuertabelle"), the latter being provided by the cantonal authorities to the employer (as per the link quoted above).
If you change your canton of employment your "Tarif" remains the same (unless you are being divorced, widowed or have a(nother) child at the same time). Yet your actual tax at source might change if the new canton of employment applies a different tax table.
I verified this with the tax at source dept in Zurich. They told me that the employer has to apply the tax table from the canton where you live (assuming this is a different canton) only if the Zurich-based employer also has an office location in the canton of residency of the employee. The logic being that in this case the Zurich-based employer has to deal with non-Zurich rules anyway. If that's not the case the Zurich-based employer is free to apply the Zurich tables (default) or the employee's home-canton tax tables.

Hi!
I have read the whole thread and others, but I still have a question as to how to proceed.
What happens if you:
- live in VAUD
- work in GENEVA
- your employer has retained the "impot a la source" with the rates corresponding to GENEVA (salary less than 120000 CHF/year).

Are you obliged to submit a tax declaration?
If yes, do you have to send the "declaration simplifie"? or you use the normal tax declaration?

Or you just wait until they send you a bill?
Has any of you been in a similar situation?

Thanks a lot!
Best,
any

It also depends on if you are married to a Swiss, and the canton.

As soon as I got married, living in canton ZH, they refunded all of my withheld taxes, and I had to fill out forms and pay normally. I was making less than 100k at the time.

When I moved to Ticino in '90, they went to the quellensteuer, until they realized that I made more than 100k, and then they refunded the money and made me fill out forms and pay normally.

(I had a B during all of this)

Tom

Thanks for your reply Tom,

actually we are talking about a single person with a Permis B living in Vaud and working in Geneva (taxes are lower in Geneva, of course).

Can anybody recommend the best procedure in this case? Fill in the simplified tax declaration? Just wait? Can one get in trouble for not filling a tax declaration in a case like this?

Thanks again and good night,
Any