United will face Middlesboro away on Saturday May 2 with a 12:45 kick off after a shake up of the reds fixture list.
The match was scheduled for 15:00 on May 2 but was moved to Sunday 16:00 when Sky Sports chose it for TV coverage.
But it has been changed back to Saturday so United have a day extra to prepare for their Champions League semi final second leg match against Arsenal at the Emirates Stadium on Tuesday May 5.
For the Boro game, United got 3,148 tickets, costing £32 for adults, £19 for over 65s and £17 for under 18s.
All away-end tickets have been sold and applicants can check their booking history to see if they got one.
Home-end tickets go on general sale here on April 21, priced at £29 to £37 for adults, at £19 to £27 for over 65s and at £17 for under 18s.