Mount is currently on £75,000-a-week at Chelsea and has now agreed terms with United.
However before then, Chelsea made a final attempt to convince Mount to stay with a new offer worth £200,000-a-week. But it still fell short of what the England international was seeking.
Mount's Blues deal has a year to run.
Relations with management have also become strained, with Mount now ready to leave his hometown club for Old Trafford in the coming days.