Q: A civil servant depends on his monthly salary to meet the needs of his living expenses as well as other necessary expenses, such as the costs of his marriage, preparing, furnishing, and paying the rent of an apartment for residence and so on. He deposits what remains of his salary in one banking company and by the end of the year, he pays the due Zakah (obligatory charity) on the total sum he saved. He had been doing this (Part No. 8; Page No. 337) for a long period of time: about 12 years. He is a religiously committed person and observes the Five Obligatory Daily Prayers and believes that Zakah is a Rukn (integral pillar) of Islam but he did not pay the Zakah due on him for some years. It is not out of his denial of its obligation but out of laziness. He sometimes pays only a portion of the due Zakah and keeps the rest until he has forgotten the number of years during which he did not pay the due Zakah and the sums of money that he used to own during these years.After his Tawbah (repentance to Allah) for having delayed the payment of Zakah, he regrets the years when he was lazy and did not pay it. Does his Tawbah exempt him from paying the Zakah for the past years on the grounds that Tawbah deletes the past sins? If not, how should he calculate the Zakah after he forgot the exact number of years and the sums of money that were with him during each of these past years? May Allah reward you with the best in this life and in the hereafter.