if u pay quellensteuer you will generally pay too much tax and have the right to fill in a return if ur income is more than 120k p.a.

this income can include rental income from abroad for example.

otherwise if u make pillar 3 payments to an additional pension you can fill in a return on this basis too.

whatever happens the quellensteuer should be adjusted towards year end based on your final accrued income for the year if you stay at the one employer. If you look at the tax tables for your commune/canton you can check this.

When i wanna fill in a return I just make out I have additional income from abroad i wanna 'declare' especially if in your 1st year it's partial and then they send you a return. worked for me here in zurich and bern since i got here and i got it every year since with 3-7k refunded per year even without 3rd pillar.

7% pension matched by your employer is excellent. Minimum can be lower depending on age so be happy.

Or you don't like saving?

Otherwise marry a Swissie so you no longer pay tax at source or wait 5 years for your C permit

HTH