Credit

From Tardis Wiki, the free Doctor Who reference

A credit is a generic term for a monetary unit. Many worlds and civilizations have described their money with the term. While they are not the same system, they often (but not always) refer to a currency system that operates electronically, rather than using currency (i.e., notes and coins).

Examples of monetary systems

The Stoish civilisation, for example, had credits which were stored on "Credit Cards'". The Doctor said that £1,000,000 was equal to 50,000,056 credits in the early 21st century, meaning that the average Sto credit was roughly equivalent to 2 pence. (DW: Voyage of the Damned)

Credits was used in various Human societies.

The Inter Minorians and Lurmans used credit bars that were blue. One bar represented one credit. (DW: Carnival of Monsters)