On 1974-04-16 the route was diverted to run anti-clockwise in Mid Levels via Caine Road, Seymour Road and Robinson Road to utilise the newly opened bus lane along westbound Caine and eastbound Robinson, the first in Hong Kong. On 1985-02-01 the terminal was transferred to Connaught Square and on 1987-04-06 to a permanent bus terminus under Exchange Square. On 1993-09-01 the route was transferred from CMB to Citybus, together with 25 other routes. Route 12 was designated a full air-conditioned route on the same day.
In 1994 Citybus proposed the merger of routes 12 and 12M, and even issued a passenger notice about it, before the plan was cancelled due to strong opposition from residents in Mid Levels. After the completion of the Central-Mid-Levels escalators, the patronage of the route started to decrease. On 1995-09-20 the terminal was changed for the last time to the new Central Piers. In 2003 Citybus again proposed the merger of route 12 with another route, this time with 3B, but was again cancelled due to opposition. Between 2003-04-18 and 2004-08-30 the route passed through Admiralty to deal with the cancellation of M16.
In 2008, Citybus once again proposed that the route be cancelled, citing rising fuel prices and increasing operating costs.