Voters will have the final say if the withholding tax on interest payments is abolished or not.
Parliament approved the abolition last year, but a coalition of left-wing parties have collected 60,000 signatures to force a referendum.
The withholding tax works by keeping back 35% of money paid in interest – its returned after filing a tax return. The idea is to cut down on evasion.
But the government maintains it hampers investment.
Opponents say it benefits large firms and the wealthy and does nothing for ordinary people and only widens inequality.