Thoughts:
Banks would be quite loath to lend to anyone they didn't think would pay them back. Travellers with no collateral wanting a zillion credit loan to fix up and operate a tramp freighter would be met with a eyeroll and shown the door.
Reputation, trust, and collateral would mean everything.
People personally moving funds from world to world would probably use some kind of letter of credit system, a letter from bank to bank. The issuing bank would confirm that an individual has the funds on deposit, and affirm that it would transmit said funds to the receiving bank via x-boat network after notified that the letter of credit has been redeemed. The receiving bank would then issue the funds to the Traveller bearing the letter, because they know that the bank that issued the letter will transfer the funds. The receiving bank would make a record of the transaction and the letter bearer's identity that would stand up in court, and issue the funds either physically or into a planetary account.
Businesspeople would probably instruct their bank on their world to deposit funds in a trusted bank on the destination world, via x-boat transmission. The bank would tell a businessperson when the funds would arrive, and issue a letter stating that the funds were issued on this x-boat on this date to arrive on approximately this date (and that the issuing bank is good for it if the transmission somehow doesn't arrive). Then the businessperson would begin his trip. The x-boat would arrive before him and the funds would be waiting in a local account when he reaches the destination world.
Physical currency would be moved by Imperial Navy detachments of sufficient strength and power to deter any player-characters pirates or other ne'er-do-wells. That could be a reason for Imperial Navy fleet movements within sectors and subsectors. It could neatly link up with the Imperial Navy showing the flag, delivering hard currency, rotating fleet elements, and doing military exercises. Hostile forces wouldn't know if it's the money fleet or a battle fleet on rotation. Hmm, adventure ideas abound...
Imperial credits might not be used by ordinary people. Residents of a world would probably use local currency, money you can buy groceries with, and if they're going to travel to another world that doesn't accept the local currency of their world, they change money into Imperial Credits, in the form of bills, traveller's checks, or bank transmissions and letters. The Imperial Credit could be something like a reserve currency, in the sense that all transactions between Imperial worlds are on the Imperial Credit standard and the transactions are done only with Imperial Credits (except by special arrangement between worlds). Travellers, Imperial military and government personnel, Imperial nobility, interstellar merchants, and other spacefarers would probably use the Imperial Credit among themselves, at starports, and in the areas close to starports, but ordinary people who don't travel between worlds or live/work near the starport would probably never see Imperial credits. It might be like trying to buy coffee and a sandwich at a little cafe in a rural Italian village using World Bank Special Drawing Rights.