He is not sure whether his father’s Hajj was valid; can he do Hajj on his behalf after his death?
Question

My father did Hajj once on foot nearly forty years ago, and he did ‘Umrah twice, the last time was at least three years before he died. He was a man who could not read or write, and I do not know how he did this Hajj. Do I have to do Hajj on his behalf? What do you think concerning that?.
Praise be to Allah.Hajj is only required once in a lifetime, and the basic principle concerning its actions and rituals is that they are valid, so no second Hajj is required. But if you do Hajj on behalf of your father it will be a naafil deed, and there will be great reward in that for you and for him, if Allah accepts it from you. 
And Allah is the Source of strength. May Allah send blessings and peace upon our Prophet Muhammad and his family and companions. End quote. 
Standing Committee for Academic Research and Issuing Fatwas 
Shaykh ‘Abd al-‘Azeez ibn ‘Abd-Allah ibn Baz, Shaykh ‘Abd al-Razzaaq ‘Afeefi, Shaykh ‘Abd-Allah ibn Ghadyaan.