Personal currency store and bank facility, universally carried.
In the high-technology environment of the Third Imperium, the methods of financial transfer and storage familiar to 20th century observers are no longer practical. There is no way that a person's bank balance can keep up with their interstellar travels; if every X-Boat leaving every system carried the financial status of all the system's inhabitants, the X-Boat would have to be the size of a dreadnaught to carry the data banks - and that still would not aid those worlds without the X-Boat network !
However, the high technology of the Traveller universe comes to the rescue here - with the personal Cashcard. This is a direct descendant of the bank machine cards and credit cards of the 20th century; but it is an electronic device.
The Cashcard appears much like a standard credit card - it is a little larger (5" X 3") and thicker, and has a small numeric keypad and a thermic pattern scanner on one side, and a magnetic computer interface (Imperial standard) on the other. There is usually a company insignia (of the card's maker) on one side and the owner's name on the other. The card is manufactured specifically for the individual (quite often as an 18th or 21st birthday present) and cannot be transferred.
Each card is (effectively) the owner's personal bank. It keeps track of his current balance, and automatically pays from that balance to designated recipients when required.
The card's mode of use is as follows: If two people wish to make a transaction, the payer places his right thumb (for humans; different versions are available for alien customers) on the thermic scanner, which reads his print and recognises it. (If it does not, the interloper receives a mild electric shock). He then enters the amount to be paid out on the numeric keypad, mates the card with the payee's card via the interface, and presses the TRANSMIT key. The circuitry in the cards then debits the appropriate amount from the register of one card and adds it to the other. A record can be kept on some models of card as to what transactions have been made with who for how much.
On worlds of tech level 8+, universal computer terminal communications mean that it is possible to transmit a payment to anywhere in the system via a standard visphone.
There are, however, certain situations in which cash money is the only way of dealing with a financial transaction. The cashcard makes its first appearance at Tech level 7, becoming widespread at tech level 8; before that, money is handled purely in cash Credits. This has led to the survival of the bank, although in a much modified form. An Imperial bank is a place where cashcards are made and formatted for an individual (a highly complex procedure requiring skills of Electronics-6, Robotics-2 and an electronic template issued by the banking company, or a cashcard maker robot). However, a bank's main function is to "buy" cash for cashcard credit - in effect, change Credit bills into the universal money. This usually entails a variable commission, by which the banks make their living. Of course, they will also exchange the other way, providing local currency for those who require it.
At tech level 13, the robot bank appears. This is a large robot, usually installed in a building (although there are some free-roaming configurations, generally armed and armoured like a warbot), capable of recognising and changing money from anywhere in the sector in which it is operating (the size of the robot determines its maximum currency capacity, but it is never less than 1,000 different types) These units are usually found in starports, although more technically advanced worlds have them more generally deployed. A variant of this is the heavily automated (but still manned) central bank with several hundred robot remotes - humanoid robots capable of changing money and in constant communication with the master system.