A kitty bank can be used (t) to store gold. This can be done multiple times, and each time it will transfer gold by the rate of the value of the type of bank, as well as increase the weight of the bank by 0.1s.
The types are: 500, 2k, 10k, 50k, 500k, 5M, 100M, and 500M.
If you have a lot of gold to put into a low type kitty bank, you can speed up the process like this: bring up the tools menu, select the kitty bank, press a number from 0-9 to assign the bank to that hotkey, close the tool menu and then hold down the hotkey you selected to rapidly fill up the bank.
They all seem to weigh 0.5s regardless of type, this allows the player to work out how much is inside.
Example: A kitty bank(500gp) that is 1s would be holding 2,500 gold. 1s - 0.5s (initial weight) = 0.5s; 0.1s = 500gp (bank type), so 0.5s = 2500gp.
Abbreviated formula is: Total Gold = [(Current Weight) - 0.5] * (Bank Type) * 10
However, using cursed flying scrolls to increase the Kitty Bank's weight does not increase the gold amount inside.
To retrieve the gold, you will have to Throw it on the ground to break it, causing a pile of gold equal to the amount stored to appear. It is advised that you throw it onto the same square you are standing, or a square with another object on it, to prevent your pets picking up the gold before you. However, this also is a method to transfer spare money to pets to train their potential, if you wish.
The kitty bank is also useful in that you can safely store your money, from which it shall not be deducted should you die. Storing gold will also reduce your taxes, since every 1k of gold on your character increases your taxes by 1 gold.
A funny thing is, the kitty banks always have about 2-140 gold in them which is removed when you make your first deposit, so if you find an "empty" one and you have no use for it, simply break it open.
Another alternative would be to sell the "empty" Kitty Bank which would give you more gold than just throwing it.
Note that even though kitty banks aren't labeled as "precious", they still can't be inherited via genes.