Thank you, I’m still pretty new to all of this and hope to develop a better understanding. So what is the SA103F boxes for? And where can I find this on a self-assessment tax return? 
is there a full list of explanations for categories and sub-categories, detailing what comes under allowable and non-allowable expenses? 
Home-office expenses is also another one that seems to be coming up as non-allowable expenses? Why?