A study of Quranic verses and Hadiths shows that unlike in other faith, in Islam paying Zakat is not just a moral recommendation to encourage people to do charitable acts and avoid parsimony and stinginess.
According to Islam, paying Zakat is a Wajib (obligatory) act that has been commanded by God and ignoring it is a sin and one who denies it is an unbeliever.
In Islam, the cases in which Zakat should be paid and how it should be paid have been clearly defined.
The responsibility of collecting Zakat lies with the Islamic government and those who refuse to pay it would be reprimanded.
In an Islamic society run by an Islamic government, those who refuse to pay Zakat would be confronted.