Dower amount is also known as haq mehar in Islam. It is the consideration of marriage contract in Islamic Law. There is a famous story about dower amount from the Era of Caliph Umar Farooq (RZA).
There was a time in his era when Muslim men started marrying Jew and Christian women as Muslim women were demanding heavy amounts of Dower Amount (Haq Mehr). On that the Caliph decided to fix the amount of dower so that Muslim women get a chance to get married. The Khalifah gathered people in the Mosque and addressed them of his intentions. On that a muslim lady said that
If Allah has not fixed the amount of dower, who is umar fixing it?
The Kaliph did not fixed any amount of mehr (dower) on that. It means that Dower amount is right of wife, she can demand anything from her husband at the time of marriage. However, if a man is not able to make payment of dower promptly at the time of marriage then such amount can be made deferred.
There are two kinds of dower amounts in Islamic Law. One is Prompt Dower (Moajjal) and the other is Deferred Dower (Ghair Moajjal). The Moajjal Amount of dower is paid at the time of marriage(Nikah). The other type of dower is payable after marriage. The wife cannot claim deferred dower amount according to Mullah's book on Muhammadan Law and PLD 1980 KHI 477.
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Salman Yousaf Khan