In the US, the official holiday is Sunday, Dec. 25. The Federal government is giving government employees Monday, Dec. 26 off as the Christmas holiday. However, non-government employers do not have to do that.
Most retail establishments will be open on Dec. 26, as will a lot of restaurants. Most of the people working office or desk jobs will likely have Dec. 26th off, as many employers follow the Federal holiday schedule. There is no Boxing Day holiday here.
While lots of places do close down or go to skeleton crews for the week between Christmas and New Years, just as many do not. I have some not-so-fond memories of one job where I worked until 5 pm Christmas Eve, drove three hours to my family's house, and spent less than 24 hours there so that I could drive three hours back Christmas night, as I had to be at work at 8 am on Dec. 26. It was a) a state government job and b) at a university which was pretty much closed down for the week, but my boss insisted that someone be there at all times, and as the newest hire, the privilege fell to me for three years on a row. Then I got a new job.