Upon the death of a person, it is a common practice to make Fateha. Contextually, Fateha is the recitation of a few Aayaats of the Qur'aan followed by a Du'aa for the deceased.
There are innumerable number of Ahaadith expounding the virtues of reciting the Qur'aan and making Du'aa. There are also many Ahaadith on Isaal-e-Sawaab (sending reward to the deceased). Surely, the deceased eagerly await for rewards from his beloved wife, parents and friends by them making Du'aa for his forgiveness, giving charity, etc. on his behalf.
However, in order for the deceased to benefit from the gifts of his beloved, they must be channelled to him in the correct way, the way of our beloved Prophet (Sallallaahu Alayhi Wasallam). During the time of the Prophet (Sallallaahu Alayhi Wasallam), many deaths occurred. It was his noble habit to comfort the bereaved families and widows. Many Sahaaba (Radhiallaahu Anhu) enquired from the Prophet (Sallallaahu Alayhi Wasallam) about Isaal-e-Sawaab (sending Sawaab to their deceased). It is not proven on any one occasion that the Prophet himself practised or ordered the customary practise of Fateha (7 days, 40 days, and 100 days). Had the customary practise of Fateha (7 days, 40 days, and 100 days) been of any significance, he surely would have at least practised it or ordered its practise at least once in his lifetime.
To emphasise and carry out a particular practise not proven in Shari'ah, for example, Fateha leads to distortion of Deen. Many people may regard the practise as necessary and an integral part of Deen as is the case among many unwary people today. Any practise which leads to a possible distortion of Deen is prohibited and a major sin. Obviously, such a practise leading to sin invokes the anger of Allah. How can such a practise benefit the deceased?
The only way to benefit the deceased is to send Sawaab to him by carrying out acts of virtue, for example, reciting Qur'aan, making Du'aa for him, giving charity, etc. as advised by our beloved Rasul (Sallallaahu Alayhi Wasallam). May Allah Ta'ala bless all our Marhooms and grant them Jannatul Firdaws.