Bank

The Bank is the name of the Island and its corresponding unique Building. By interacting with the Bank the player can invest in or take gold from the bank. Gold left in the bank gains interest on a day-by-day basis. The starting daily interest before any skills is 1%.

You also can use the bank as an "Emergency Fund" it will bail you out if you overdraft your charges charging you $1000 gold. You must pay the bank back the $1000 prior to your next overdraft or you will be bankrupt and immediately lose the game.

Skills and Perks
Bank interest rate can be increased by +1% / +2% with the skill:

Achievements
Investing in the Bank for the first time awards the achievement:

Getting bailed out by the Bank for the first time after going Bankrupt awards the hidden achievement: