HSBC is to transfer 840 IT jobs from the UK to other sites around the world, including India, China and Poland.
Most of the affected jobs are based in Sheffield, Tankersley and London - with the transfer set to be completed by the end of March 2017, the bank announced.
John Hackett, chief operating officer of HSBC UK, said: "In our investor update in June 2015, and many times since, we have stated that we are targeting significant cost reductions by the end of 2017.
"As part of a global relocation exercise, around 840 non-customer-facing IT roles will transfer from the UK to other sites around the world by the end of March 2017.
"The UK will continue to play an important role in HSBC's global IT infrastructure, employing several thousand IT professionals."
Dominic Hook, national officer of the Unite union, said: "HSBC's decision to axe so many IT jobs is as ruthless as it is reckless.
"For almost a year, staff have been left in the dark about their futures, only to be told that before being shown the door they're expected to train someone in India or China who will do their job for less money.
"It's a deeply cynical move by a bank which wants to be an 'Employer of Choice'.
"Offshoring IT jobs to so-called low cost economies is extremely short sighted. As IT glitches across the banks continue to prove, it is ultimately the customers who will suffer the consequences.
"Unite will continue to support our members throughout this process and work with our sister international trade unions to end this cynical race to the bottom."