The Red Devils signed Blind, 28, from Ajax in 2014.
Blind impressed at Old Trafford, however, the defender struggled to get regular game time under Jose Mourinho last season.
And it’s understood United have agreed an original £14m fee with Ajax, which could rise to £18.5m with add-ons.
Blind will sign a four-year deal with the Dutch giants.
The Dutch defender was a regular under Louis van Gaal, but his game time dropped under Mourinho.
Blind’s exit could trigger an overhaul at Old Trafford.
Matteo Darmian is expected to leave United this summer, while Luke Shaw’s future remains up in the air.
The England international has been publicly criticised by Mourinho, who claimed the former Southampton star always needs instructions.
United have been busy in the summer transfer window, with Fred, Lee Grant and Diogo Dalot heading to Old Trafford.