Most people claim, when they realise that they lost out on benefits, that they were not advised to sign on for credits. To overcome this, SW get people to sign an acknowledgement form that they have been advised of the option (it's such an important thing, SW staff really emphasise it). Your friend should call in and ask to see this to confirm that he was advised or not. If not, then he may have a case to ahve his claim backdated to January and get credits too.