Brentford are set for a windfall of at least £7million should James Tarkowski join West Ham.
The Hammers are chasing a deal for the Burnley defender, who moved to Turf Moor in 2016 for a fee of £3m, and are currently offering the Clarets a deal worth £27m.
Should the 27-year-old be sold this summer, the Bees will be due 27.5 per cent of any profit made on the sale.
And with West Ham expected to go back in with a third offer, they could be set for more than £7m.
Tarkowski - who hopes a move away from Burnley would improve his chances of adding to his two England caps - made 74 appearances for Brentford in his two years after joining from Oldham in 2014.
Burnley first quoted the Hammers £50m for Tarkowski, having rejected a bid of £40m from Leicester last summer, but it is understood that an offer of around £30m with add-ons would be enough to get a deal moving.
David Moyes, whose funds have been boosted following the sale of Grady Diangana to West Brom, is desperate to add quality and experience at the back.
Alongside Tarkowski, the West Ham boss is also looking at Bologna's Japanese defender Takehiro Tomiyasu, who can at play right-back, centre-back and in a holding midfield role if needed.