Swansea City will receive about £2m as part of the deal which took Joel Piroe to Leeds United should the Elland Road club win the Championship play-offs.
Leeds signed striker Piroe from Swansea for an undisclosed fee last August.
It is understood the transfer could eventually be worth more than £10m to Swansea, with a £2m chunk resting on Leeds winning promotion back to the Premier League.
Leeds go to Norwich City in the play-off semi-final first leg on Sunday.
Daniel Farke’s team missed out on automatic promotion after a slump in form which saw them lose four of their final six regular-season games.
They eventually finished third, six points behind second-placed Ipswich Town.
If Leeds overcome Norwich, they will face either Southampton or West Bromwich Albion in the Championship play-off final on Sunday, 26 May.
Dutchman Piroe, who scored 46 goals across two seasons at Swansea, has scored 13 times in 46 Leeds appearances, 32 of which have been starts.