Can someone pay Fidya for Salat of a dead person who missed some Salat in his life?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

There is no ransom to be paid on behalf of a dead or a live person who missed some prayers.

But, if the dead person did not give up performing the prayer during his lifetime, then it would be beneficial – Allah willing – to do some good deeds and to ask Allah to grant him the reward of those good deeds.

For example, a live person can give money as a charity, and then pray to Allah to grant the reward of this charity to the dead person. According to some scholars, it will be beneficial for the dead, if a live person presents him the reward of any good deed, even prayer.

Thus, depending on the above opinion, a live people can pray with the intention of granting the reward to a dead person.

For more benefit on deeds that benefit a deceased person after his death, please refer to Fataawa 83855 and 84938.

Allah knows best.