News of Errington's retirement is spreading on RBS's Insite intranet.
RBS said: “Mike will be leaving RBS, but there is no timescale at this stage.”
Errington is one of the old guard at RBS and has survived several cost-cutting exercises and major IT problems.
In February 2014, sources in the finance IT sector told Computer weekly that Errington will be a casualty of RBS's cost-cutting plan, known as Project Cook. At the time, RBS told Computer Weekly that Errington's position had not changed.
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The IT head is nicknamed "Offshore Errington", due to his propensity to send IT jobs to low-cost, offshore regions.
Read more about IT at RBS
In 2012, problems with IT systems at RBS left customers with no access to their bank accounts for days.
The glitch in the CA7 batch process scheduler ended with 12 million customer accounts frozen. Customers were denied access to funds for a week or more as RBS, NatWest and the Ulster Bank manually updated all account balances.
Then, in December 2013 - on the busiest shopping day of the year - IT problems stopped customers making online and card payments.
In the same month, RBS CEO Ross McEwan said the failure of systems was unacceptable and blamed years of underinvestment in IT for the issues.
"For decades, RBS failed to invest properly in its systems. We need to put our customers' needs at the centre of all we do. It will take time, but we are investing heavily in building IT systems our customers can rely on," he said.