Ipswich chairman David Sheepshanks hopes striker Darren Bent's emerging England career will earn Town an additional fee from Charlton. The 21-year-old moved from Portman Road to The Valley in the summer.
"There is a sell-on clause in the deal, should Darren move from Charlton for a fee higher than they paid for him," Sheepshanks told Town's website.
"And if he plays in a competitive international for England, we will receive a substantial sum."
Bent received his first senior call-up at the weekend after Crystal Palace striker Andy Johnson pulled out with a hamstring injury.