I've just read a letter addressed to my partner. unknown to me, she has had a single person claim ongoing despite us moving in together in May 2012. she has been overpaid by over £8000 and we are more than worried by this. I have asked why this hadn't been sorted, she couldn't really say, besides arguing wont solve this. according to calculators the amount of tax credits we WOULD have had is very close to what she has received. She is naive with money I believe and has buried her head somewhat to this , now we're up the creek so to speak. I don't believe her intentions were fraudulent or deliberate more silly. however I have told her she needs to get on the phone and sort this out tomorrow. some information about our household: Living as a couple since may 2012 Parents to two children whom live at our address our income from May 2012 - July 2015 was as follows: Income support - £160 odd fortnightly (for both) Child Benefit - £34 per week Carers allowance ( paid to myself looking after a relative ) - £62 per week. Child Tax Credit ( claimed as a single person ) - £117 per week appx: £1170 per month. I have read about a potential for offsetting the overpayment against the correct claim amounts had it been done. which would likely drop this overpayment bill to below £500. I am trying to sort this out as I have just started a new full time job and want everything to be above board. £8000+ of tax debt will cripple us a family. I fully accept this is a significant mistake on our behalf and had I known , I would have acted sooner. any advice would be greatly appreciated. many thanks.