The contract, which supplies services to Barclays from Glasgow, Beeston and India, employees 518 full-time staff and 350 temporary staff.
The four-year contract was signed in 2000. It was renewed in early 2006 and again in late 2006. The existing contract will expire on 30 September.
Barclays could retain staff for a year as the work is transferred, but once the work is integrated back into Barclays, Siemens said, "redundancies are unfortunately inevitable".
A Barclays spokeswoman said, "We have been in ongoing discussions with Siemens regarding their contract which ends this year and have decided not to renew this.
"As we have not yet reached an agreement with Siemens on the detail of how we will manage the exit of the contract, it is too early to confirm how we will integrate this work back into Barclays. However, at this stage we do not plan on continuing to base the current activity at the Glasgow and Beeston sites in the future.
"Staff have been advised that once the activity is integrated back into Barclays, their roles will become redundant."
A Siemens spokesman said it is working with the Public and Commercial Services Union to support the staff affected. The company added, "Whatever the outcome, redundancies are unfortunately inevitable though we hope to achieve these on a voluntary basis and would always look for redeployment opportunities for our staff where appropriate".