Boss misusing furlough

Rayman69

This past year I've been working part time with top-up furlough payments to supplement my reduced wage. I was receiving on average £290 a month. Over the last few months I've been working around 20-21 hours a week but noticed on all my payslips that my boss is only paying me for 12 and letting furlough pay the rest, and now my weekly wage is only £210. (I just want to add that altogether I'm being paid for 24 hours of work per week, which is 3-4 more than I am working, but this is not enough and is much less than I am used to receiving). This means my boss is saving around £80 a week from my paycheck and I'm only just covering my living costs each month. It's a small business so there's no HR department I can go to, and I'm hesitant to report it because I need this job. I also know if I ask my boss, he'll have no problem lying about it. There was a brief time around December where he stopped claiming furlough, then restarted again in January. I'm wondering if the reduced amount I'm getting is based on a new calculation from that time, and whether I am actually out of pocket because of that, not because of what my boss is doing.
My question: How do I find out if my boss's actions are in fact reducing my pay without reporting him? 

Jeremy535897

If you are working 20 hours a week you should be paid for those hours, not 12 hours.