ZURICH ¨C Many of Switzerland¡¯s foreign millionaires will be watching nervously on Sunday as voters decide whether to scrap one of the country¡¯s biggest tax perks for expatriates.

Switzerland¡¯s system of charging foreign residents with no gainful activity in the country a lump sum based on their living expenses, instead of taxing assets or income, has helped make it a popular home for the super rich.

Five Swiss cantons, including Zurich, have abolished the lump-sum tax, but the left-wing Social Democratic Party gathered the necessary 100,000 signatures to force a vote on doing away with it at the national level.

The ¡°Stop the tax privileges for millionaires (abolition of lump-sum taxation)¡± campaign has been conducted largely in the shadow of two other initiatives up for a vote on Nov. 30 ¡ª introducing limits on immigration and boosting Switzerland¡¯s gold reserves.

But high-profile Swiss residents like Formula One chief Bernie Ecclestone and Russian billionaire Viktor Vekselberg will be following the tax result closely. A ¡°yes¡± vote could see them hit with higher tax bills.

French tennis players who live in Switzerland, including Jo-Wilfried Tsonga, caused a stir by incorrectly answering questions about Switzerland, such as its capital, Berne, in a quiz conducted by French sports newspaper L¡¯Equipe last week.

Polling by Berne-based research institute suggests the tax initiative will likely be rejected, with many voters concerned about the economic implications of a ¡°yes¡± vote. Switzerland pocketed 695 million Swiss francs ($717.53 million) from the tax in 2012.

Scrapping the tax, introduced to attract wealthy pensioners to Switzerland, would be the latest blow to the country¡¯s status as a tax haven. Switzerland effectively ended its long-cherished banking secrecy in May by agreeing to join other countries in sharing tax information.

If the lump-sum charge were scrapped, accounting firm KPMG Switzerland¡¯s head of international private client services said many wealthy foreigners would seek a better tax deal elsewhere.

¡°Some of our clients, I assume, would stay in Switzerland, the ones that are really personally attached to Switzerland, that enjoy the Swiss lifestyle,¡± Frank Lampert said.

¡°Others, I¡¯m quite sure, would leave Switzerland because their main consideration when choosing Switzerland was to find a mild tax regime.¡±