Legal advice: What can I do if a customer won't pay?

I sold a tractor to another farmer, but now he won't pay for it - what can I do?

Steering wheel and levers in the cab closeup. Industry

Dear Stephen,

I am a full-time farmer and I also operate a small agricultural machinery and contracting business from the yard outside my sheds. I recently sold a tractor to another farmer I've dealt with before.