OVO Energy says it does not know the "precise number" of jobs which will be lost in the Borders as part of UK-wide cuts.
The energy giant has announced the closure of the Selkirk office, which contains 380 employees.
Staff will be invited to apply for voluntary redundancy, an OVO spokesperson said.
Remaining employees will be "relocated" or will work from home, said the spokesperson.
They added: "We will know more at the end of the voluntary redundancy window which begins today."
Meanwhile, a union representative has issued a statement on the nationwide cuts.
UNISON regional organiser Gerry Crawley said: "Any job loss at this time is deeply regrettable but UNISON will continue to work with SSE/OVO to try and ensure that any job losses are through a voluntary redundancy process.
"UNISON welcomes the fact that, through early engagement, 700 jobs that were going to be off shored to South Africa will now be maintained within the UK."
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