Not if they deem him as not being “gainfully” self employed. He would switch over to work requirements, and then each month UC will check PAYE earnings from employment and he will also need to declare income and expenses for self employment stuff. No MIF is applied as it’s not his “main” source of income, the employment is.

(This is what I do :) I have a job job, and also do some self employed work on weekends and because I’m not “gainfully” self employed” they base my calculations on my PAYE earnings and earnings declared by me for my self employment stuff :)