I am sharing with you this prayer, a copy of which is in my personal organizer. I find it handy to have this with me all the time so that I could immediately pray for a person as soon as I found out that he/she has passed away:
Responsory for the Dead
V. Do not remember my sins, O Lord
R. When you come to judge the world by fire
V. Direct my way in your sight, O Lord, my God.
R. When you come to judge the world by fire.
V. Give him/her eternal rest, O Lord, and may your light shine on him/her for ever.
R. When you come to judge the world by fire
V. Lord have mercy.
R. Christ have mercy; Lord have mercy.
All:
Our Father… sin against us.
V. Do not bring us to the test.
R. But deliver us from evil.
V. From the gates of hell.
R. Deliver his/her soul, O Lord.
V. May he/she rest in peace
R. Amen.
V. Lord, here my prayer.
R. And let my cry come to you.
V. The Lord be with you.
R. And also with you.
V. Let us pray.
Lord, welcome into your presence your son/daughter N., whom you have called from this life. Release him/her from all his/her sins; bless him/her with eternal light and peace; raise him/her up to live for ever with all your saints in the glory of the Resurrection. We ask this through Christ, our Lord.
R. Amen.
V. Give him/her eternal rest, O Lord
R. And may your light shine on him/her for ever.
V. May he/she rest in peace.
R. Amen.
V. May his/her soul and all the souls of the faithful departed, through the mercy of God, rest in peace.
R. Amen.