Around 1,200 G4S security staff who deliver cash and coins have voted to strike in December, prompting fears of shortages ahead of Christmas.
The industrial action could impact the supply of cash and coins at banking clients such as Barclays, HSBC and Santander, and supermarkets including Tesco, Asda and Aldi.
The GMB union said it will be the first ever strike at G4S after union members voted to walk out, with a 97% vote in favour of action.
It said the strike is scheduled to take place from 3am on December 4.
G4S Cash Solutions initially offered members a part pay freeze and have since tabled an offer of a 4% increase and lump sum bonus based on contracted hours.
The security giant was taken over by American firm Allied Universal for £3.8 billion last year following a takeover battle.
Eamon O’Hearn, GMB national officer, said: “There are low paid workers doing a dangerous job, transferring the cash so many of us still rely on every day.
“All they are asking for is a wage they can live on, that they can feed their families on, that they can treat their children this Christmas on.
“G4S Cash staff provide an absolutely vital service. If they walk out, we can expect genuine cash shortages over the festive period.”