Dundee United are in line for a £250,000 bonus if Reading win promotion to the Premier League.
Former Tannadice striker Noel Hunt, 27, netted the club a £600,000 fee from the Championship outfit three years ago.
However, a clause in that transfer deal included another payment of £250,000 if Reading then achieved promotion.
The Berkshire side are due to face Cardiff or Swansea in a play-off semi-final and will enjoy a windfall if Reading can reach England's top flight.
Irish goalscorer Hunt had four years at Dunfermline before joining United in 2006 and playing there for two seasons.
He scored 13 goals in his first season at Reading but made only 12 appearances in 2009/10 due to a knee injury.
His 10 goals this season have helped his team to fifth place in the Championship, with a play-off place guaranteed.