Chief executive Jonathan Westhoff said the society was moving to the Point North development, at The Waterfront, near the Merry Hill shopping centre, in a former base of banking company egg.
There are no plans for the society to change its name after the move.
The news comes after the Express & Star revealed the society was in talks on moving from its iconic West Bromwich High Street home in January. After an extensive fit-out, it is hoped staff will move by autumn next year.
The news has been greeted with shock and anger in Sandwell and fears over staff re-location costs for its six-mile move, however bosses at Dudley Council has welcomed the move.
Mr Westhoff said: "The brand is what the society's name represents: our goods and services, rather than a geographical location.
"We're keeping ourselves in this heartland., keeping ourselves in our home roots.
"I really hope our members think this is a strong move for us. It gives us the necessary growth capacity for the coming years and that is the strongest message we can put out for our members and staff."
The society has been in West Bromwich for 160 years. Bosses said its current home, in a 1970s block, was no longer fit for purpose or its future plans.
Chiefs then considered a new base at West Bromwich's £75million Providence Place development, next to telecommunication giant BT's regional business centre.
But bosses said the asking price was higher than anticipated and looked towards Point North, which Mr Westhoff said was ideally suited as it was designed for a financial services company.
The society has now agreed with Richardsons Capital to lease 70,000 sq ft of space at the six-tier canalside block.
Mr Westhoff said the speed of the move was central to the decision, as relocating to Providence Place would have taken 14 months' time at the least.
He also conceded the deal with Richardsons Capital, which involved negotiations with senior figures at Dudley Council as well, was cheaper.
He said: "Over the 15-year lease it does work out better for us at Point North."
Point North will initially accommodate around 500 staff, with room for future expansion and growth, and provide support services for the West Brom's 38-branch network.
There will also be an administration centre providing a direct service for savings accounts, mortgages and investments.