Hong Kong handles around 70 percent of all yuan transactions outside the Chinese mainland. While the total value of transactions that the special administrative region handles continues to grow, its share of total transactions globally is dropping as other centers expand.

Addressing the ASIFMA conference, Vincent Lee, executive director of the Hong Kong Monetary Authority, said Hong Kong remained the largest offshore yuan center in the world. About one-third of the mainland's external trade was carried out through Hong Kong, he added, with about half of all inward investments, as well as outbound direct investments out of the mainland, moving through the city.

"In the coming years, in view of the increasing use of the RMB internationally... there will be more opportunities for the use of the RMB in Hong Kong, given our close ties with the mainland."

The yuan real-time gross settlement system in Hong Kong moves about 800 billion yuan every day.

"We are working with other financial centers to grow corporate awareness of RMB business," Lee said. "RMB business has grown very fast in the past few years but ... we still need to do some more work to promote awareness, particularly outside of Hong Kong and outside Asia.

"We will continue to work with these centers to grow the business and to promote awareness," Lee said.

Yuan business is growing very fast at the moment, he added, but it is still quite small internationally.

A number of countries with offshore yuan centers are increasingly important to this trade, suggesting the use of the yuan is spreading globally.

Between February 2013 and February 2015, offshore centers outside Hong Kong saw their share of yuan settlements rise from 17 percent of the total to 25 percent.

Through clearing facilities provided by Chinese banks such as the Industrial and Commercial Bank of China or Bank of China, clients can convert foreign currencies directly into yuan without converting into dollars.

Other financial centers around the world have set up offshore yuan centers. The biggest is London, a global financial center, and the introduction of trading and clearing services in yuan has not been difficult.

London accounted for 42 percent of global foreign exchange trading, larger than any other financial center, said Madera of UKTI.

"Being a global center means that players in the UK are looking at global opportunities," she said. "Chinese inward investment needs to be competitive. Sometimes we forget this."

Rapid growth in the number of these centers is creating new opportunities for investors and powering the overseas use of the currency.

It is still early and hard to say exactly how overseas use of the yuan will evolve and who will be first to take advantage of this trend. What is certain is that it is happening.