Under the customary Muslim law, a person cannot bequeath more than one-third of his property by will. But if he has married under Special Marriage Act, then he can will away entire property, and succession is governed by Indian Succession Act, and not the Muslim personal law i.e. Shariah Act 1937.The remaining 2/3 share should be made available for distribution amongst the heirs. Even for bequeathing the 1/3rd share, the Muslim has to obtain the consent of the other heirs. Relevant Case on this point is: GULAM MD.vs. GULAM IIUSSAIN, AIR 1932 PC 81 ... Held in this case that, bequest in favour of heirs without the consent of other heirs is invalid.
Bequeathable One-third:-- It means a third of the estate of the testator as is left after the payment of the funeral expenses, other charges and debts of the deceased (testator). All schools of Muslim Law except the Ithana Ashari School lay down that bequest of more than one third unless consented to by the heirs is invalid or a custom or usage so permits.
Formalities of Wills:-- Muslim law requires no specific formalities for creation of a will. It may be made in writing or oral or even by gestures. Though it is in writing, it need not be signed by the testator and attested by the witnesses (Ramjilal vs. Ahmed, AIR 1952 MP 56). It is necessary that the intention of the testator should be clear and unequivocal.