Money

Money, or cash, (TV: The Categories of Life) was a medium of exchange used to facilitate transactions of goods or services. (TV: The Man Who Never Was)

According to the Twelfth Doctor, "Nothing is protected like money," because it was protected by the best firewalls in the universe. (TV: The Husbands of River Song)

The Sevateem had no concept of money. (AUDIO: Death-Dealer)

In Great Britain, the earliest printed money came about in the 18th century. Before then, wealth was generally stored as gold, gems, or various other high-price commodities. (AUDIO: Death on the Mile) By the 1960s, the UK used pounds, shillings and pennies. (TV: "An Unearthly Child")

The Doctor's money
The Ninth Doctor told Rose Tyler that he could not pay for chips as he had no money. Teasingly branding the Doctor a "tightwad", Rose proceeded to pay for their chips. (TV: The End of the World) Later, however, the Doctor proved able to obtain money from a cashpoint aboard Satellite Five in the year 200,000. Providing a card of unlimited credit to Adam Mitchell, the Doctor deemed it "pocket money". (TV: The Long Game)

Entering a diner, the Twelfth Doctor told the waitress that he had no money, but he could play the guitar for her, which he accepted. Unbeknownst to him, the waitress was actually his former companion, Clara Oswald, the memory of whom he had lost. (TV: Hell Bent)