You are carrying out a "dynamic risk assessment" each time you turn up to a customer whether you know it or not. So for those that say I've never carried out a risk assessment well you have been. You know the potential hazards may change with boxes or furniture or washing lines being in the way or the weather conditions with rain, ice, low sun etc affecting how you work. For this you don't need to carry out a paper exercise just like a postman wouldn't, common sense is required however.
(Site work I would imagine is down to what they require.) I'll download the form for next week!