Royal Bank of Scotland said it has resolved problems that led to customers being unable to withdraw cash from some ATM machines.
NatWest and RBS customers have been unable to withdraw cash from other than the banks' own cash machines, the bank said.
Customers have taken to Twitter to complain about the problem.
RBS' spokeswoman Nicky Harris said customers should be able to withdraw cash from RBS and NatWest ATMs, but that they are experiencing problems while using other banks' machines.
NatWest bank customers have taken to social media to complain about being unable to withdraw money from their accounts. Many have voiced their frustration on Twitter.
Umm....4 non natwest cash machines & all of them refuse to give money! Only one that worked was a natwest...problems again? @natwest_help
If you're a #NatWest customer you can't get money from Link machines, only NatWest branches are working.
A spokesperson said the bank is investigating the issue.
Mobile customers of Barclays, NatWest and RBS are enduring a difficult final day of the month - payday for many Britons - after being locked out of their banking apps.
All three banks announced problems with their apps on their Twitter accounts, saying:
We’re aware that there are issues with accessing our Barclays Mobile Banking app; this is being looked into on an urgent basis. 1/2
We’re aware of some issues on our Mobile Banking service and are working hard to fix them. Sorry and thanks for your patience.
If you’re having difficulty with our mobile app, online banking, telephone banking and ATMs are all working normally.
The trio urged their customers to use online banking, telephone banking, ATMs or visit a local branch to deal with their money issue or pay a bill.
Royal Bank of Scotland will offer three-month mortgage repayment breaks to customers with flooded homes.
Full details, including how to apply for the scheme will be released tomorrow by the group, which includes NatWest.
It said it would also send specialist business support teams to affected areas in coming weeks to help small businesses with short-term financial problems as they carry out repairs and suffer lost trading income.
NatWest have been struck by another technical blunder which has left some customers short-changed on their monthly interest payments.
Some NatWest and Royal Bank of Scotland (RBS) customers checking their E-Isa balances found they had been updated with just a few pence worth of interest in some cases.
A spokeswoman for RBS/NatWest described the error as an isolated incident and said customers' balances are being updated with the correct amounts as a matter of urgency.
Those who have found a mistake do not need to contact the bank as it will be automatically fixed.
While this latest failure is not IT-related, the bank has been beset by a string of technological errors in recent months.
Just days after that incident, the bank's websites were the victim of a cyber attack that left some customers unable to access their accounts.
NatWest has apologised to customers after its online service were disrupted by a 'denial-of-service' cyber attack. In a statement, a spokesperson said:
Due to a surge in internet traffic deliberately directed at the NatWest website, some of our customers experienced difficulties accessing our customer web sites this evening.
This deliberate surge of traffic is commonly known as a distributed denial of service (DDoS) attack. We have taken the appropriate action to restore the affected web sites.
At no time was there any risk to customers. We apologise for the inconvenience cause.
As reports emerge of online banking issues with NatWest, ITV News has asked whether you were affected tonight.
Yes I was affected by it. Wish I never banked with this bank worst ever.
I just used mine no problems.
Nope I have logged onto my NatWest account twice today and transferred money not a problem.
Join in the conversation on the ITV News Facebook page
NatWest has said that its online banking system is now working after customers reported problems transferring money and using the site.
Sorry if you couldn't use Online Banking earlier. It's now working again, thanks for your patience.
NatWest customers are continuing to report issues with transferring money as the online banking system apparently faced a glitch tonight.
Asked whether Mr Curry was receiving any error messages, he responded: