Approach to sign

Can anyone please explain the criteria which makes "Approach to sign" youngsters for a compensation fee possible?

A mixture of their age, type and length of contract I think but not sure.

Thanks

I think that it is the wage per year multiplied by the amount of time spent at the club.

Sorry maybe I wasn't clear, I want to know what factors mean the "Approach to sign" option is there or not...?

Thanks

No worries. It is 6 months of the contract left except for English clubs trying to sign players from English clubs where it is only for the last month of the contract.

Thanks, I was asking about about youngsters though...

I've seen plenty with 2,3,4 years left on their contract but you can "Approach to sign" with a compensation fee

You can approach most players on a youth contract, but not all??

Its because they are on a youth contract, and not a "proper" contract. All players under 17 are on a youth contract, any club can approach the youngsters at any point, unless the club have agreed a deal with the player to sign pro terms on their 17th birthday. I believe youth deals run until their 18 years old then they are either released or offered pro terms.

Yes, all the one's I couldn't approach have provisionally agreed a f/t contract.

Thanks for your help!