A quasi-resident is a taxpayer subject to withholding tax residing abroad who wishes to claim effective expenses and other deductions in his tax return.
To qualify for the status of quasi-resident, at least 90% of your worldwide income must be taxable in Switzerland.
In the case of a married couple, the incomes of the spouses are added together and 90% of these incomes must be taxable in Switzerland.

If you are in this case, then you can benefit from the subsequent Ordinary Taxation (TOU).