Customers struggling to access banking services and call centres took to social media to complain about the issues.
Some Lloyds Bank customers reported being logged off during a session and receiving error messages.
One customer wrote: "Your internet banking is down and your call centre keeps cutting me off."
Halifax mobile banking users also reported problems logging on.
A Halifax customer posted on Twitter: "I've been trying for an hour now to reach you by phone and online. Neither are working.
"All I want to do is find out the current balance on my c/card. This shouldn't be this hard. The website keeps crashing, and the automated phone line doesn't tell you your balance."
Both banks have apologised for the issues.
Lloyds and Halifax both later posted updates on Twitter, saying: "We know some of you are having issues with online banking at the moment.
"We're sorry for this. We're working to have it back to normal soon."
According to Downdetector, more than 3,000 people have reported issues while trying to access Lloyds Bank services in the last few hours.
Around 1,700 Halifax customers have also reported problems with their banking services.
