Since the mid-1990s, the Federal Reserve has estimated, cash has been in decline.
The Los Angeles Times noted cash not only faces competition from credit cards but smartphones, which give businesses opportunities to advertise to customers before they pay or to offer coupons.
But the Times says the rise in such payments raises concerns about security and privacy, including worries hackers could take money without customers noticing.
"The bottom line is that as the mobile payment system evolves it is important ... to provide proper oversight so that these payments can be secure and convenient," Sen. Tim Johnson, D-S.D., said in March, when Congress opened hearings on such payments.
Twelve percent of cellphone users had made a payment through their phones, the Federal Reserve found in March. And nearly two-thirds of technology experts surveyed by the Pew Center on Internet and American Life said in March they expected mobile payments to be greater than payments with cash and credit cards by 2020.
"We are, I think, on a precipice of some fundamental change in the way money is exchanged between consumers and businesses," said Rep. Shelley Moore Capito, R-W.Va.