You represent Rosita and Roger, a married couple.  They are both computer software engineers with unique expertise.  They have significant clients all over Michigan, Illinois, Ohio, in Las Vegas, in Mexican factories near the US border, in London, England, and all over Germany.  They had a project in Las Vegas lasting 3 weeks.  While there they celebrated Rosita's sister visited with her family. They hosted an amazing dinner party celebrating the sister's 40^th birthday, charged to their room.  Other meals were charged to the room during the stay.  They deducted all Las Vegas expenses, including the Starbucks coffees and cakes they bought at the airport.  This was done on last year's return.  You are retained to prepare this year's return. What is your duty once you learn of this issue?