year-end office closing; last business day of the year
Typically refers to the final working day of the year for government offices and many companies, often December 28. The complementary term is 御用始め (first business day of the new year).
See also: 御用始め
Today is the year-end office closing, and government offices became quiet from the afternoon.
On the last business day of the year, we finish up the year's work.