As the use of cash declines and digital payments increase, a new independent review has been set up to look at the impact on consumers.
The Access to Cash Review will look at the impact of new technology, including contactless cards, over the next five to 15 years and examine future needs.
It will be chaired by the former head of the Financial Ombudsman Service, Natalie Ceeney.
Ms Ceeney said there was a need to make sure no-one was left behind.
She added: “The rise of contactless and digital payments has changed the relationship between cash and consumers.
“Many people in the UK have already made a shift to paying for most things digitally, but at the same time, there are between two and three million people across the UK who are entirely reliant on cash.”
The review is funded by Link, the UK’s biggest network of cash machines, but is independent from it.
It will spend the next six months gathering information.
Link said consumer groups, community representatives, small businesses, industry and the general public would all be able to contribute their views.
Harry Rose, money editor of Which?, said: “We’ve seen hundreds of ATMs closing across the country, with more under threat, which risks excluding the millions of people still reliant on cash in their daily lives.
“This review is much-needed and we’ll be pushing to ensure that everyone’s access to cash is properly protected.”
Last month, it emerged that debit card payments had overtaken cash use for the first time, as contactless technology takes a firm hold on day-to-day spending.
A total of 13.2 billion debit card payments were made last year, a rise of 14% on the previous year, according to banking trade body UK Finance.
That outstripped the 13.1 billion cash payments made, as the use of notes and coins dropped by 15%.
An estimated 3.4 million people hardly used cash at all during the year.
Young consumers, aged between 25 and 34, were most likely to make contactless payments. Those who shunned cash entirely were also most likely to be among this age group.