The HSBC banking app has collapsed, stopping people from making transfers or payments.
People who tried to use the app have been shown a warning telling them to come back later.
HSBC said: ‘Our mobile app is currently unavailable.
‘Please check back later.’
On Twitter, one HSBC customer called Neil Cooper wrote: ‘All HSBC online services down (again)? Personal and Business accounts not accessible through website or via mobile apps.’
The HSBC Business support account on Twitter admitted it was having problems in a tweet which said: ‘We are aware of some issues with the service, and our I.T department is looking into this at the moment.’