These days, the Chief Post Office serves as the main Information and Visitors Centre, has Starbucks as a ground floor tenant, and provides some office space on the upper floor. The structure is registered with the New Zealand Historic Places Trust as a Category I heritage building.

The building originally housed the postal department as well as other Government and administration offices. In 1881, New Zealand's first telephone exchange was installed in the building. The building was extended in 1907 to the west by adding a third gable; up until that point, it had two symmetrical façades. The extension was designed and supervised by Burrows. When the new Government Building opened at the eastern end of the Square in 1913, the postal services remained and the building became known as the Chief Post Office.

In the 1930s, the post office was threatened by demolition, as more space was required. Construction of a new post office didn't start until 1989, immediately to the south of the existing building. The seven storey building dominates and impairs the historic structure, and parts of the old building had to be demolished to make way for the high rise.

Reputed to be a replica of London's Great Clock of Westminster, a working, free standing, four faced turret clock was installed in 1879 within a clock tower. Underneath the east facing clock face is the Royal coat of arms of the United Kingdom. Notable for being unreliable, an electric clock was eventually installed to control the visible faces as slave clocks.

While at one time it chimed on the hour and at the quarters, after the mechanisms were damaged in a 1980s fire, the clock became silent.

The building suffered minimal damage in the 2010 Canterbury earthquake, and only minor damage in the February 2011 Christchurch earthquake.