Fiqh-us-Sunnah Volume 003, Zakaat and Fasting, Fiqh 3.057.

Section : Delaying of Zakah (Payment) Does Not Void It.

Ash-Shaf'i holds that anyone who does not pay zakah for a number of years must pay it all together. Whether or not he is aware of its obligation or he happens to be in a Muslim or non-Muslim land, makes no difference. Based on the opinion of Malik, ash-Shaf'i and Abu Thaur, Ibn al-Munzhir says: "When unjust people rule a country and the people of that country do not pay their zakah for a number of years, then their new leader should take it from them."