As salamu alaykum,
In the book Fiqh us Sunnah it states as one of the deeds that benefit the deseased:
Prayer (salah). This is based on a report by Ad-Darqutni who said that "a man asked, 'O Allah's Messenger! I had parents whom I served while they lived. How can I be good to them after their death? ' The Prophet, peace be upon him, said, 'Verily, among the good deeds that you can do after their death is to offer prayer (salah) for them when you pray for yourself and to fast for them when you fast for yourself'."
Does this mean that one can offer a salaat for example of 2 rakaats and then convey its reward to the deseased ?
Is this prayer what is called Salat al Walidayn by Ibn Abidin in his Radd ul Mukhtar as he said there in the section of nafila prayers; that Shayk Ismail has said from a work Sharh Shiratul Islam that salaat for ones parents (mother/father salaat) also one of the mandub salaats is.
Was salaam

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.

It is permissible for the Muslim to perform two Rak'aat and gift their reward to the deceased, whether the deceased is his father or anybody else, and this reward reaches and benefits the deceased – Allaah Willing. The reward of prayer, like other acts of worship, can be gifted to the deceased. However, the issue is controversial among scholars and what we mentioned is the preponderant opinion. For further information, see Fataawa 84938 and 89131.

As regards what the Hanafi scholar Ibn ‘Aabideen mentioned, it belongs to the recommended prayers, which include “prayer for parents”. This prayer may (in Hanafi texts) refer to performing two Rak'aat and gifting their reward to one's parents.

Allaah Knows best.