Short answer
Yes. Charity given on behalf of a Muslim who has died reaches them and benefits them, and you are rewarded too. The four schools agree on this. A lasting charity (sadaqah jariyah) in their name, such as a well or copies of the Quran, keeps benefiting them for as long as people use it.
Gifting the reward of sadaqah, and of other good deeds, to the deceased (isal al-thawab) is permitted and reaches them; it is mustahabb (recommended), especially from children for their parents. Debts and other duties of the deceased should be settled from the estate first.
The four schools agree on this.
Explanation
A man told the Prophet ﷺ that his mother had died suddenly and asked whether she would be rewarded if he gave charity for her. He said yes. On this and similar hadith, the four schools agree that charity given on behalf of a dead Muslim benefits them. (They differ on some other deeds, such as the reward of reciting the Quran, but not on charity or dua.)
Ways people do it:
- Giving to the poor and making the intention that the reward is for the person who died.
- A lasting charity in their name: a well, a share in a masjid, copies of the Quran, or funding a student. See sadaqah jariyah.
- Paying off their debts, which is among the most urgent things you can do for them.
- Making dua for them, which the Quran itself teaches (see dua for deceased parents).
No special words are needed. Intend in your heart that the reward goes to them, or say, "O Allah, give the reward of this to so-and-so." You can include several people, and the Hanafi scholars say each receives the reward in full without your own being reduced.
Be careful with the estate. Until it is divided, it belongs to all the heirs. Charity can be given from it only with the consent of every adult heir, and never from the shares of children. Charity from your own money has no such limit. To leave lasting charity yourself, include it in your Islamic will, up to one third.
The evidence
Quran, Surah Al-Hashr 59:10
وَٱلَّذِينَ جَآءُو مِنۢ بَعْدِهِمْ يَقُولُونَ رَبَّنَا ٱغْفِرْ لَنَا وَلِإِخْوَٰنِنَا ٱلَّذِينَ سَبَقُونَا بِٱلْإِيمَٰنِ وَلَا تَجْعَلْ فِى قُلُوبِنَا غِلًّۭا لِّلَّذِينَ ءَامَنُوا۟ رَبَّنَآ إِنَّكَ رَءُوفٌۭ رَّحِيمٌ ﴿١٠﴾
And [there is a share for] those who came after them, saying, "Our Lord, forgive us and our brothers who preceded us in faith and put not in our hearts [any] resentment toward those who have believed. Our Lord, indeed You are Kind and Merciful."
Believers pray for those who died before them, and their prayers benefit them.
Sahih al-Bukhari 1388
Sahih... فهل لها أجر إن تصدقت عنها قال نعم ...
"Will she be rewarded if I give charity on her behalf? He said: Yes."
Charity given for a dead parent reaches them.
Sahih Muslim 1631
Sahih... إذا مات الإنسان انقطع عنه عمله إلا من ثلاثة إلا من صدقة جارية ...
"When a person dies, his deeds end except for three: a lasting charity, knowledge that benefits, or a righteous child who prays for him."
Lasting charity keeps benefiting a person after death.
Where the ruling is recorded
- Radd al-Muhtar, Kitab al-Salah, chapter on funerals, on gifting reward to the dead. A person may gift the reward of any good deed to another, living or dead.
- al-Hidaya, Kitab al-Hajj, chapter on hajj on behalf of another. States the Hanafi principle that one may give the reward of one's deeds to someone else.
- al-Majmu', Kitab al-Jana'iz, on what benefits the dead. Agreement that charity and dua benefit the deceased.
This answer is pending review by the scholars on our team. Quran translation by Sahih International. Hadith Arabic from the standard editions of the six books and the Muwatta, with gradings as recorded there; the English is our own rendering. Spotted a mistake? Tell us.