The Mirror says a fee has now been agreed worth £50m - but Palace's other star man, Zaha, was a crucial component in the deal.
The two clubs are believed to have discussed the sell-on clause attached to former United man Zaha as part of the deal.
Eventually, it was agreed the 25% sell-on clause would remain in place as United look set to cash-in if the winger leaves Palace this summer.
Zaha returned to Selhurst Park in January 2015 after an unsuccessful spell at Old Trafford.
United inserted a sell-on clause in the transfer and could be set for a £15m windfall if Zaha moves on.