How is my first Swiss tax return calculated if I moved here mid-year?

If your tax liability starts partway through the year, generally only the income actually earned during that period is taxed. Regularly recurring income, such as salary, is annualised to determine the applicable tax rate, which is then applied to your actual income. Deductions are generally pro-rated according to the duration of tax liability, though counted in full for rate purposes. Cantonal practice and individual circumstances can affect the position.