When a death occurs, several surahs get recited, and which one depends largely on where you are in the Muslim world. Yasin in South Asia and much of the Arab world. Al-Mulk in some communities. Al-Fatiha almost everywhere. The evidential footing for each of these differs quite a lot, and they are worth separating.
Surah Yasin
The most widespread choice, resting on the report from Ma’qil ibn Yasar instructing that Ya-Sin be recited over your dead. That report is genuinely disputed: graded weak by a number of specialists on grounds of an unnamed narrator and inconsistency in transmission, accepted by Ibn Hibban and others.
There is a further question of whether the wording refers to the dying or to those who have already died, which changes the practice substantially. Our article on reading Surah Yasin for the deceased sets out both sides.
Surah Al-Mulk
Al-Mulk is often mentioned in the same breath, and here a distinction gets blurred.
The narrations about Al-Mulk, recorded in collections including al-Tirmidhi and Abu Dawud, describe it as a surah that intercedes for the person who recites it, and it is widely associated with protection from the punishment of the grave. The established practice built on these reports is that a living person recites Al-Mulk regularly, often nightly before sleeping, for their own benefit after death.
That is a different thing from reciting it on behalf of someone already buried. The commonly cited reports concern your own recitation during your lifetime. Worth knowing, because the two get conflated.
Surah Al-Baqarah at the graveside
There is a practice reported from Ibn Umar of reciting the opening and closing verses of Surah Al-Baqarah at the graveside during burial. Scholars have differed over the strength of this and over whether it establishes a general practice.
It is on record and has been acted upon within some schools, which puts it in a different category from the numbered formulas circulating online, though it is not among the strongest evidence either.
Surah Al-Fatiha
Reciting Al-Fatiha for the deceased is near universal in practice and is often what people mean when they say they read something for someone who has died.
Its basis is the general question of whether the reward of recitation reaches the dead, which is exactly where the schools diverge. The Hanafi and Hanbali schools generally held that it does. The Maliki school and the earlier Shafi’i position were more restrictive, though later Shafi’i scholars took a more permissive view, particularly where recitation is followed by supplication.
The pattern worth noticing
Every one of these practices depends on the same underlying question rather than on the merits of the individual surah: does the reward of an act performed by the living reach the deceased?
Scholars have answered that differently for centuries, with serious argument on both sides. Anyone who tells you the answer is obvious is not representing the scholarship accurately, in either direction.
What everyone agrees on
If the disagreement leaves you unsure what to do, two things are agreed across every school without exception, and they are not consolation prizes.
Supplication for the deceased. Asking forgiveness and mercy for someone who has died is established beyond dispute and explicitly encouraged. Every position accepts that it reaches them.
Charity given on their behalf. Supported by clear reports, accepted universally, and it has the additional quality of doing good in the world while it does good for them.
Whatever view you hold on recitation, these two are available to you, cost nothing in terms of scholarly controversy, and are what the tradition points to most clearly when someone dies.