From what I can see you were self employed at one time, and being on low wages were getting working tax credit, chances are that like me, you were not earning enough to pay tax, which is why they are now saying you were not self employed, so fight them, find old customers, suppliers, adverts, receipts, even bank payments/ PayPal etc for materials, prove to them you were self employed. I got stung for hundreds of pounds tax fines because I didn't send off a tax form saying I owed £0 tax. Once you have gathered the proof that you were self employed, ask for a review from tax office, but get CAB involved too. You might face fines for not filing the right tax forms, and sadly they don't accept ignorance of the rules as a defence. The fines should be less than repaying all the working tax credit. Remind them that if you hadn't been self employed you would have been on unemployment benefit and all the added benefits, so why would I have claimed to be self employed? Surely they have to prove their side, but they do try and bully people into a voluntary repayment schedule. Best wishes