Economy
The Imperium protects and encourages trade between systems. This includes supporting a financial system for conducting trade easily and quickly.
There are multiple ways of conducting monetary transactions within the Imperial financial system as well as the numerous ways that worlds conduct business and ways things are handled outside of the Imperium.
Imperial Star Ports of a certain class or higher and all Scout and Navy bases have a branch of the Imperial Bank that will perform most transactions. Many space ports on Imperial worlds will have a branch of the Imperial Bank.
Local financial systems can take just about any form but most Imperial worlds will support the Imperial financial system to some degree. Sometimes it is just a bank in the capital that will exchange CRImps and local currency. Sometimes banks and businesses support all the common forms of Imperial cash and credit.
The smart card or credit stick
There are some devices that require obtaining autherization for each transaction (like a modern credit card or on line banking). There are other devices that are just a means of identifying the apropriet acount from which funds will be provided (like old credit cards and checks). There are also smart devices loaded with a set amount and all transactions and the current balance are maintained on the device. This last group of smart devices are detailed here.
Devices can have numerous varieties.
A device could be loaded with actual funds (bought like a visa prepaid card).
A device could be loaded with a set amount of authorized credit.
Security
For security, some devices are only capable of a limited number of transaction. For security, devices usually have an experation. For security, some devices not only electronicly track transactions, but are physicaly marked or punched to indicate transactions. For security, some smart cards and credit sticks only have the ability to subtract funds and no amount of software hacking can add funds since the hardware is incapable of doing so.
While some devices are extremely reliable, nothing is tamper proof. Obviously, doing so is a crime.
Some versions of these devices are only provided by Imperial banks. Other devices can be loaded/created by certain high level authorized representatives, like TAS or trusted local financial institutions. There are some devices which can be acquired from a local merchant or even a ships Steward for paying crew.
Some cards are bearer versions - anyone possessing the card can use it. Most cards have some form of security from a simple pin to biometric authentication.
Usage
Even on a low tech world, some businesses may have a machine of the appropriate TL for conducting business using these cards. However it's more common for a traveler to use the most secure version of a smart card or credit stick and stop at the Imperial bank at the star port to obtain a version of the local financial medium.
Some cards are for Imperial bank use only but held by the account holder or a representative or even sent via courier. Businesses can't take them, they can only be used at another Imperial bank. This is usually for the transfer of large values when the normal means for financial institutions to convey information is not conducive to expedient transactions.
Once funds or credit is on a device, it's like cash in your hands. Some people do forgo using these devices and opt to use Imperial credits. If you lose the device recovery options can vary, based on the type of device, from as simple as requesting a new one, to long delays as the different bank branches all synchronize transaction logs and account information, to "sorry, not my problem".
Merchants, crew, and other seasoned travelers usually don't put all their eggs in one basket. They tend to have multiple credit devices loaded with varying amounts.
It's a good idea for a merchant to know where they are going and to plan for their financial needs before they depart.
Pretty much all the ways we are doing things now are still possible in the future.