Banks and Banking
In the modern world, banks are like investments - you put money in, the bank invests it, and eventually you get your money back plus some interest. The security a bank provides is also nice, but the fact is the bank is paying you for the privilege of making money off your money. Not so in the Known Worlds.
In the Known Worlds, characters go to a bank to secure their money, not to invest it; after all, large quantities of coin can cause a lot of trouble. They have five major options: the League Bank, the Brother Battle, the Imperial Bank, the Scravers' Guild and noble houses/cathedral coffers.
The League Bank is the largest bank in the Known Worlds, with branches on every world. Money deposited in the League Bank - generally, the League charges 5% of deposits - is accessible at any of its branches in these times of peace, though remote branches will charge additional fees. (That has not always been true in times of war.) Money in the League Bank is very secure; it is the daring thief indeed who steels from the Reeves' Guild, thought it has been done.
The Brother Battle bank began when the Order kept money safe from pilgrims, but it is now the second-largest bank in existence. The Brothers charge 10% of deposits, and money in Brother Battle coffers is available from any Brother Battle bank branch - which is to say on every planet. Stealing from the Brother Battle is just a bad idea; so far, no one has ever survived an attempt.
The Imperial Bank, founded by Alexius, is the youngest bank, and it charges only 3% of deposits. Unfortunately, the Imperial Bank presently only has branches on Byzantium Secundus, Tethys, Stigmata and Criticorum - though they are expanding.
The Scravers' Guild is not officially in the banking business, but as the banks above often ask questions potential clients might not want to answer they have quite a following among the criminal class. The fee the Scravers charge is directly proportional to the power of the Scraver keeping the money safe, and also bears a direct relationship to the security of the funds: with the Scravers, you get what you pay for. Keeping money with the local Scraver capo might be as little as 2-3%, but securing any meaningful sum is going to run 15-25% of the total sum.
Noble houses will also keep money safe for their family members, as will the local Cathedral for priests in the area - and neither charges any fee for the privilege. There is a catch, however; in both cases, there is the possibility that funds might be withdrawn by someone besides the person who deposited them. Siblings have been known to drain the accounts of their family on many occaisons, and the local parish priest may borrow from monies entrusted to the sacristry to cover needed improvements to his Church or even just gambling debts incurred when the Pancreator was looking the other way. Still, it's safer than just stuffing 'birds under a mattress.