The anticipatory tax is a so-called securing tax. Its purpose is not to finally collect 35 % but to encourage the honest declaration of capital income: anyone who lists their interest and dividends in the securities schedule of the tax return gets the deducted 35 % back. Anyone who conceals it loses the money, hence the securing effect.
How it works: when a Swiss bank pays interest or a Swiss company distributes a dividend, it retains 35 % and remits it to the Federal Tax Administration. The investor therefore receives only 65 %. Via the tax return they reclaim the 35 %: for individuals resident in Switzerland this runs through the cantonal tax authority, which offsets or pays out the amount with the tax bill.
Who is affected and when: everyone with taxable capital income from Swiss sources, from a savings account with interest, to shares with a dividend, to a lottery or pools win above the exemption limit. For foreigners and foreign income, double-taxation treaties apply; the refund then runs through special procedures and is often only partly possible. Foreign income in a Swiss custody account can be claimed for credit of foreign withholding taxes via form DA-1.
What to watch for: the refund requires complete and correct declaration, "forgetting" income leads to the definitive loss of the 35 %. The refund claim also lapses (for individuals three years after the end of the calendar year in which the income fell due). Anyone holding securities should keep all the bank's tax statements (tax voucher) and enter them in the securities schedule.
A fiduciary or tax advisor prepares the securities schedule, ensures the full refund, and checks the credit via DA-1 for foreign securities. For the mere declaration of existing custody accounts, the effort usually falls within the scope of the ordinary tax return (no guarantee).