A minute’s silence is due to be held across the UK at noon on Friday to mark a week from the date of the attack.
Perthshire Couple, William (Billy) and Lisa Graham were murdered at gun point by IS in Tunsia as they were relaxing on the beach enjoying a late birthday present.
Thomson and First Choice said in a statement that all 30 British people killed were its customers.
“The whole company would like to extend our deepest sympathies to the family and friends of those involved in this tragic event,” it added.
“Our main focus now is to ensure the families of the deceased and our customers who have been injured receive all possible support at this incredibly difficult time.”
Provost for Perth and Kinross, Liz Grant, said: “I am greatly saddened to learn of the deaths of William (Billy) and Lisa Graham. On behalf of all of Perth & Kinross Council I would like to say that our thoughts are with the Graham family at this tragic time.
“I would also like to pass on the condolences of the Council to all of the families affected by this horrific attack both here in the UK and abroad.
“On Friday, the Council will observe a minutes silence to remember and pay our respects to the victims and their families.”
Work forces are to volunteer and allow employees to pay their respects.