I have an artist working on some things for me and I've just found out that they are 15.
In the UK, can a 15 year old legally sign over copyright to another person?
The assumptions made by me are 1. A minor can hold copyright 2. A minor cannot enter a legally binding contract.
A minor can own property including copyright.
A minor can also enter into contacts that are genuinely in their interest - note that this is an additional protection not afforded to adults. A minor needs the permission of their legal guardian to enter a contract and while this can be implicit in your circumstances it would be wise to make it explicit.
Notwithstanding, a minor may revoke a contract (if possible - they can't if they have drunk the milkshake, for example) while they remain a minor and for a reasonable time after they attain their majority. If they do this you would lose the copyright and they would have to refund your money. This is just a risk you will have to bear and factor into what you are willing to pay.
As an aside, there are three "properties" your contract needs to deal with: any physical artifacts (like a painting), the copyright and the moral copyright.
Yes, see Chaplin v Leslie Frewin publisher Ltd (1966). Chaplin entered, then failed to revoke a contract for the transfer of copyright.
This falls under a more general exception about the provision of services when aligned with the benefits of the minor.
