Employment and Support Allowance overpayment

Hi, I hoped you may be able to help me. I'm currently appealing for ESA to the Upper Tribunal which has now been referred back to be decided again by a new First-tier Tribunal. In August last year I received a letter from ESA Bury St Edmunds, Wolverhampton, asking for £408.60 for an overpayment they thought I owed them for a period of work I did as a cleaner at a University. I was entitled to ESA during this time as an earlier tribunal decision had given me entitlement to ESA from 19/6/18 to 19/619. The finance department of DWP had telephoned me in 2014 asking about having any additional earnings and I told them I was a self-employed artist but this wasn't regular money and wouldn't have gone over the ESA work limit. I replied back to the overpayment letter saying that I didn't owe any money because I had no additional earnings from self-employment during the time I was working at the University and supplied them with a bank statement of the period concerned to show them this. They didn't contact me again after this so I though the issue had been resolved, until last Friday when a new letter arrived saying that to make a decision about my overpayment caused by the University work, I needed to supply copies of my self-employment accounts for each year from 2015. In my opinion the issue has been resolved with my bank statement and there is no need to look at my accounts for the past five years. It also implies that they will be looking over my accounts to see if I owe them any more money. A friend said that the government are just looking to get some money back from Covid-19. I just wanted to know if by law I have to supply them with my accounts or could I just ignore this letter? I haven't received any money for ESA for about a year now and it's not in my interests to supply them with this information. Although I've only made a small amount of money selling paintings, I'm concerned they'll rack up a huge bill and I have little money in the bank. I'm really worried.
They've side-lined the main issue of whether they're paying my ESA or not and bullying me again about this. My appeal has been going on for over two years now and I'm finding it hard to cope with the constant battle I have with the DWP as well as coping with my own mental health issues, so this letter was especially distressing when I received it. Could you please give me your advice about what I can do next. Thanking you, kind regards, Lizzy

Hi Gordon, thank's for your speedy reply and alerting me to my name showing. Just wanted to clarify that because the DWP haven't paid me ESA since last June and I' appealing my case, is it still necessary to provide my accounts, you said that they may suspend my payments, but they're not paying me at the moment!! Would it still affect me receiving ESA in the future if I do eventually get back on it? Thanks again for your advice, Lizzy