Employees can write "Season's greetings and a happy New Year" or "Sincere wishes for hope, happiness and peace during the holiday season." The employee needs to make sure that he or she personally signs the card using a legible signature.
"Warmest thoughts and best wishes for a merry Christmas and a happy New Year" is an appropriate option for formal holiday wishes. A more casual choice is "May you have a very merry Christmas."
If the employee is unsure about which aspects of Christmas the boss observes, "Best wishes for peace and joy this holiday season" or "Wishing you and your family a wonderful holiday season" are both suitable messages.