Players have the option to instantly complete a building, which is under construction. This option is paid for with Credits. It can be used 2 times in 24 hours (3 if Premium account is activated, 4 if Platinum premium account is activated), for each of your Planets, separately. The cost of instantly completing buildings depends on the remaining construction time. For each hour of construction time remaining the price is 15 Credits.
You can use this option only if building construction has already started.