BP fuel stations across the UK are now able to accept card payments after a glitch which lasted over three hours.
BP had said earlier its stations were only able to accept cash and that it was directing customers to its ATMs.
The oil giant said all its sites had now returned to normal service, and it was launching "a full investigation" into what had caused the problem.
"We will monitor the situation overnight to ensure the smooth running of our operations," it said.
BP earlier said the issue had caused "a handful" of stations to close.
The company said it did not know what had caused the issue.
A BP spokesperson said the problem had started around 19:00.
"We would like to thank our customers for their patience and again apologise for any inconvenience caused during the brief outage," they added.
BP has 1,280 BP stations across the UK.
Highways England had earlier tweeted that all motorway service areas with BP fuel stations were affected by the problem.
We've been advised that all @BP_UK fuel stations across the UK are experiencing issues accepting card payments. Currently they're only able to accept payments for fuel in cash only. This is affecting all motorway service areas with BP fuel stations.— Highways England (@HighwaysEAST) July 8, 2018
Adam Johnston, who works at Spital BP station in Bebington, Wirall, said the card payment problem had been "an absolute nightmare" with "queues out the door and people struggling to get onto the forecourt".
The station had to fill out 10 forms where people were unable or unwilling to use the ATM, which required them to return and pay within seven days, he said.
He said the station was typically busier than normal BP fuel stations because it was also an M&S franchise.
"Most customers are sympathetic but some not so much resulting in arguments and a lot of stress," he added.
Heather Brogan, a customer at a BP fuel station in Southwell, Nottinghamshire, was also affected.
She had gone to buy "a handful of items" from the shop and used the onsite ATM to pay the £20 required.
" It's only a small town. People were absolutely fine about it," she said.