President Karol Nawrocki signed the bill into law after it was approved by both houses of parliament, his office said on Thursday.
The Personal Investment Accounts (OKI) are aimed at encouraging household savings and long-term investment, according to the government.
Under the law, any adult in Poland will be able to open at least one such account with a financial institution. Multiple accounts will also be allowed, including umbrella-style arrangements covering different types of investments, state news agency PAP reported.
The new rules will take effect in January.
The initiative, first announced last year, offers tax incentives to encourage participation.
Investments in savings bonds and bank deposits will be tax-exempt up to PLN 25,000, while investments in equities, investment funds and certain bonds will be exempt up to PLN 100,000.
Above those thresholds, funds held in the accounts will be subject to a tax based on their value, calculated at 19 percent of the central bank's reference rate.
Next year, the tax rate on assets is expected to be set at 0.85 percent.
Officials said the system is modelled in part on Sweden's Investment Savings Account (ISK) scheme.
Government spokesman Adam Szłapka said in May that the new voluntary financial instrument was intended to boost domestic investment, strengthen the capital market and support economic growth.
Finance and Economy Minister Andrzej Domański has said the "tax-free investment account ... will give Polish households a chance to save and invest efficiently."
Poland's capital gains tax—commonly known as the "Belka tax" after former Finance Minister Marek Belka, who introduced it in 2002—applies to income from interest-bearing assets and securities. It stands at a uniform rate of 19 percent.
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Source: IAR/PAP, prezydent.pl