A shortage of precious metals during the 15th century. This led to issues within Europe where many currencies were coins, made out of the metals that were in shortage. Since coins were made out of mostly gold and silver, the lack of these metals meant the money supply suffered.
Much of the exploration during this period was due to the need to find more metals. The discovery of the Americas aided in this effort. So did trips to India.
In the late 1400s, Luca Pacioli is said to have created double-entry accounting. This provided developed the concept of the liability. What ensued was the creation of ledger-based monetary systems. Merchants, in need of a ways of transacting, offered credit as a means of money. This was used all through Europe.
This helped to reduce some of the impact of the Great Bullion Famine although much of Europe was negatively affected.
Eventually the discovery of new mines along with newer drilling techniques cured the famine. This did not, however, end the use of a ledger-based monetary system. This is still in use today.