Yes, interest on mortgages is tax-deductible in Switzerland and will therefore reduce your taxable income. Instead of direct amortisation, where you make regular repayments to the mortgage lender, you can also choose indirect amortisation. This involves paying the amortisation amount into a pillar 3a pension account, with the mortgage lender having right of lien over the account as collateral. You can deduct payments made into the pension account from your taxable income, thereby reducing your tax burden. In addition, the capital in the pension account accrues tax-free interest. Early withdrawals are also taxed at a reduced rate.