Most Swiss citizens and permanent residents (Permit C) fill out their income tax return once a year and pay taxes afterwards. However, for newly arrived foreigners there is the Source Tax.
Who is subject?
Mainly affects foreign workers who have a residence permit L or B and border workers (Permit G) from some countries.
How does it work?
Your Swiss employer deducts this tax directly from your gross salary each month, in the same way that personal income tax withholding on the payroll works in Spain. The employer then transfers this money to the canton's tax administration. The rates applied depend on your Marital Status, the number of dependent children, whether your spouse works, and the tables of the corresponding canton (rates A, B, C...).
Amending tax return
Depending on your canton, until March of the following year you may have the right to request a correction of source tax if you have incurred expenses that are deductible (such as 3rd pillar pension plans, childcare expenses, donations, educational recycling).
Important limit: Those people with a B permit who exceed a threshold of annual gross salary of 120,000 CHF are obliged by default to file the ordinary income declaration, although they continue to be withheld month by month on account of the definitive.