The Hammers were due to make Benrahma's loan move from Brentford permanent in the summer but they have finalised the deal early to free up loan space.
A deal for Lingard has been agreed in principle between the two clubs.
England midfielder Lingard, 28, has been told a move away from Old Trafford will be sanctioned given his lack of first-team action.
Any deal required the Hammers to sign either Benrahma or Dawson on a permanent basis.
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