Update Thursday 29 September: Since we published this story, Natwest has fixed the problem. A spokesperson said: “Our Online Banking service is currently operating as normal. We apologise to those who experienced difficulties accessing the service yesterday."
Natwest customers have been left unable to make payments via its online banking service due to a technical glitch.
Customers began contacting the bank for help earlier this afternoon after encountering a "service unavailable" message while trying to pay money from their Natwest accounts to other people or companies.
MoneySavingExpert.com journalists encountered the same error message after logging into their Natwest accounts and attempting to make a payment.
A Natwest spokesperson said a technical problem was to blame: "We are aware that a small number of customers are experiencing issues making payments through online banking and we are working to get this resolved as quickly as possible.
"Our customers can still use our mobile app, visit our branches or use telephone banking as normal. We apologise to customers for the inconvenience."
Natwest hasn't said when it expects the issue to be fixed - but we'll update you as soon as we know. If you're affected you can let us know at firstname.lastname@example.org.
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What are Natwest customers saying?
Dozens of concerned customers have sought help from Natwest on Twitter after encountering the problem:
Anyone banking with NatWest today - they are having massive issues with their online banking Danielle Slatter (@mouseslatter) September 28, 2016
@NatWest_Help Are online payments down? I can't do a transfer. Live chat: "sorry all our team are busy, try again later" Neil (@neil2009) September 28, 2016
@natwest is there a problem with online banking? can login, but can't make payments. Rupert Graves (@AdUnityEU) September 28, 2016
@NatWest_Help unable to make a payment on line today. can you tell me when this will be fixed? Rich Cundill (@RichCundill) September 28, 2016