Season ticket holders with one European away credit who were turned down in the ballot can buy tickets for the Champions League final tomorrow.
From 8am to in-person callers only, "a small number" of tickets will go on sale at Old Trafford.
A club spokesman said: "A small number of supporters have cancelled tickets which have now been released for resale.
"Tickets will only be allocated to supporters who were unsuccessful in the ballot and have at least 1 European away application (credit) from this season.
"These will be allocated to personal callers at the Ticketing & Membership Services building from 8am on Wednesday 20th May
"If supporters are buying tickets for other people with the relevant criteria they must have the actual passport for all other supporters as well as their own."