Most people do not consider the copyright implications of Christmas carols.They are concerned more with last minute gifts.
But many popular Christmas carols are covered by copyright protection. Singing these songs at home in front of a small gathering does not violate the public performance right in copyright. But for those of us who are more adventuresome and desire to stretch our tonsils in public, there is a list of well-known public domain Christmas carols published at the Public Domain Information Project.
And here is a list of other well known Christmas songs still under copyright protection.
We wish you a Merry Christmas ...