Tesco has apologised for taking money from people's accounts months after they visited its Express stores.
The issue has left many customers upset as they have been charged for a number of shopping trips at once.
Some have complained of being unexpectedly thrown into their overdraft by the late charges from the supermarket.
The company said an issue with its card payments system in 300 Tesco Express stores meant that some payments had not been fully processed at the time of the shop.
Customers are furious to find that payments made in November, December and January have all suddenly been debited from their accounts, according to the website Money Saving Expert.
Laura Pidcock wrote on Twitter: "I've had payments leave my account for transactions made months ago in Tesco express store "
I've had payments leave my account for transactions made months ago in Tesco express store
— Laura Pidcock (@LauraPidcock) February 13, 2018
North London car breakdown and recovery service Vroooom Automotive wrote: "Just found out that Tesco has had card payment problems in over 300 express stores and is now starting to take payments 2 months later what a absolute joke #nothappy #anothermessup."
Tesco's chief customer officer, Alessandra Bellini, is writing to affected customers to explain the error and say "sorry for any inconvenience this may have caused".
The letter says: "We are writing to let you know that a number of credit and debit card payments did not process correctly for some customers, in a small number of our Express stores.
"You may have noticed this as an unexpected transaction at Tesco in your bank statement.
"You were accidentally not charged on a recent visit and this is a delayed payment. Rest assured, you will not have paid twice. You can view all transactions affected below."
I'm trying to gather as many people as possible who have been affected by @Tesco taking late payments this week for transactions that happened in December/January. Please do you your thing Twitter and RT this far and wide
— Sharon (@DoctorWarmflash) February 13, 2018
One shopper, called Julie, told Money Saving Expert: "I was both shocked and horrified to find out Tesco had taken three months to put through contactless transactions.
"These said transactions range from November 2017 through to January 2018. Nothing was indicated on my online statements as to pending payments and they've now presented me with these bills after nearly three months.
More from Tesco
"I run a tight budget and they have now told me that there are nine transactions that were not processed correctly and that they would take them all out now."
Adam told the site: "Taking nearly two months to send a letter out is a bit too long. I called them to say that I can't pay it all at once as this will take me overdrawn, only to be told that the money will come out of my bank in the next few days."