Brentford have been told by a tribunal they may have to pay up to £115,000 with add-ons for Myles Weston.
The Bees snapped up the out-of-contract winger this summer but the two clubs could not agree a fee between themselves.
As the 21-year-old is under the age of 23 Notts County were entitled to compensation despite the winger being out of contract.
The tribunal has set Brentford an initial £25,000 for Weston with a further £10,000 coming after every ten appearances up to a total of 50.
The Griffin Park side will also have to pay an additional £40,000 should they win promotion within two seasons, while County will also retain a sell-on clause.