The telecoms giant said that the job cuts and other measures would help it to reduce costs by £1.5bn.
It added that it would be hiring about 6,000 employees to “support network deployment and customer service”.
A third of the job reductions will come from outside the UK in its Global Services division.
Last year, BT was forced to write down the value of the Italian part of Global Services after an accounting scandal that cost the firm more than £500m.
The company also said it intended to move out of its existing central London headquarters and into smaller premises.
BT forecast a fall in revenue of about 2% for the 2018-19 financial year. It also said it was keeping its full-year dividend unchanged from last year at 15.4p a share and would freeze it for the next two years.
Shares in BT fell nearly 8% in early trading.
‘Lean and agile’
BT said it was responding to changes in the telecoms market, including “increasing competitive intensity from established companies and new entrants”.
“It is critical that BT transforms its operating model to build a lean and agile organisation that delivers sustained improvement in customer experience and productivity,” it said.
The announcements came as BT disclosed that its annual pre-tax profits rose 11% to £2.6bn in the year to March.
The firm also announced a 13-year plan to plug its £11.3bn pension fund deficit, including regular payments into the scheme and a bond issue.
Chief executive Gavin Patterson said BT was in a unique position: “We have the UK’s leading fixed and mobile access networks, a portfolio of strong and well segmented brands, and close strategic partnerships.
“This position of strength will enable us to build on the disciplined delivery and risk reduction of the last financial year, a period in which we delivered overall in line with our financial and operational commitments whilst addressing many uncertainties.”
George Salmon, equity analyst at Hargreaves Lansdown, said the job cuts and HQ move were “drastic actions”, but added that they “still aren’t going to be enough to dig BT out the hole it’s in”.
“The dividend, which was rising 10% a year not so long ago, is set to freeze for the foreseeable future, and next year’s profits look likely to fall again,” he added.
“There are silver linings here and there. For example, EE and the consumer businesses continue to grow. However, these improvements are being more than offset by challenging conditions elsewhere.
“Openreach terms are getting tougher, and the business-to-business and global divisions are having a torrid time. Gavin Patterson will have his work cut out if he’s to steady the ship.”