A technical glitch locked some current account, savings account and loan holders out of their accounts.
The bug affected one in 20 accounts, the equivalent of up to 300,000 people.
Access was blocked on the mobile app as well, meaning that these people were completely locked out.
Fixing the problem
Tesco Bank noticed the issue on Tuesday afternoon, but is unsure of what caused it.
Standing orders and direct debits were unaffected, allowing card holders to carry on using their debit card to make transactions and withdraw cash as normal.
People who have credit cards and insurance with Tesco Bank were unaffected.
As of this morning, all accounts are back online.
Tesco Bank issued this statement:
"All customers can now see their accounts online as normal. We apologise for any inconvenience caused and thank customers for their patience."
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