Thank you so much dx100uk and honeybee13 for putting things in perspective. I had been worrying myself silly over this and the possible outcomes.

Hi dx100uk, Thank you for replying. I will look up the SAR procedure and send one off for all details they hold

Hi Honeybee, Thank you for responding, I have contated HMRC three times now and spoken to three different people, each one flatly refused to discuss the debt and insist I contact LCS. I'm worried that HMRC will just take enforcement action next if I continue to ignore LCS

In 2013 I had to give up work due to chronic ill health, I notified HMRC of my changed circumstances and my tax credits claim ended. Around six months later, I received a letter from HMRC stating I had been over paid by £3,500. I called them and after explaining my circumstances they agreed to suspend repayment, they didn't say for how long, just to expect further contact in future. I have since heard nothing from them. About a month ago, out of the blue I received a letter from a debt collector agency called LCS demanding repayment, I contacted HMRC and on asking why they had not contacted me directly, I was told it was normal practice to pass debt over to a DCA who would then pass it back to them on receiving proof of inability to pay and I could expect this to happen each year. After receiving a further two threatening letters from LCS, the last being a “notice of further action” I again contacted HMRC. This time they claimed to have contacted me a number of times and as I had failed to respond they had put recovery in the hands of LCS. They flatly refused to deal with me saying I must deal only with LCS. I have read posts on here advising never to contact a DCA. I'm confused and anxious as to what I can to do if HMRC refuse to deal with it. I'm very worried about this debt and its beginning to affect my already poor health. I hope someone can advise me on the best course of action.