As is fitting in a highly commercial city, an accurate system of weights and measures governs trade. The primary financial unit is a gold coin called a Dran; one dran might be a week's work for a skilled worker. These coins are therefore somewhat ill-suited to day-to-day business, for which notes are used. These notes are issued by one or other of the large banking houses, and since the Grand Unification, they are always issued in one of two values: one tenth of a dran, or one eighth of a tenth (one eightieth of a dran). These notes are commonly referred to simply as a "tenth" and an "eighth", giving the odd result that an eighth is smaller than a tenth.
For purchases where even an eighth is too large, various local schemes are used, but none are nationally enforced. Some banks will issue notes to the value of a tenth of an eighth, which are slightly mis-dubbed "twentieths"; businesses which encourage repeat custom will more usually simply run an account for people, thus avoiding the hassle of dealing with small change. Unofficial promissory notes are well known among certain circles, but - being unofficial - these cannot be used outside the particular group in which they are valid.
By law, no banking-house is permitted to issue notes for which it does not possess corresponding drans. This has led to some difficulties when a bank has been robbed; but such an event has not occurred since the security of banks was assured by the guild of mages. The only fear is that a walker might rob the bank and leave; but the difficulty of aiming a dimension-walk makes this occurrence unlikely.