Thousands of customers who bank with Halifax, Lloyds, and RBS customers are experiencing problems with online banking on the first day of the new year.
Online banking is down for all three banks across large parts of the UK as the websites have crashed.
Halifax and Lloyds has apologised for the "issues" and a spokesman says they are working on resolving them as a priority.
In a statement both said: "We know our customers are having issues with internet and mobile banking.
"We're sorry about this and we're working to have it back to normal soon."
RBS has not yet released a statement.
Lloyds said they are working on the problem but "if you urgently need to transfer funds you can call our phone bank team on 0345 300 0000 and they would be able to look at it for you".
One customer said: "Obviously the millennium bug overslept by 20 years." Another added: "Lloyds taking the 'bank holiday' a little too literally."
