Karina Moon vividly recalls the telephone call that brought her to tears. She was stood, frozen, in the living room of her home in north Wales as a government official told her she needed to repay £11,292.75 or be prosecuted for fraud. “I broke down, I was crying,” she said. “I was gobsmacked. I was absolutely distraught because I live within the law. They made me feel like I was defrauding it.” The phone call, which came out of the blue, was all the more shocking because Moon, 62, keeps completely on top of her finances. She retains payslips going back years, carefully scrutinises the small print of benefits entitlements and can, in her own words, “budget like there’s no tomorrow”. Yet Moon, like tens of thousands of others, had fallen victim to the carer’s allowance trap. A single mother, Moon for most of the week is the sole carer for her daughter, a bright and bubbly 22-year-old who has a rare genetic condition called Bardet-Biedl syndrome. This means she needs constant care, is on the autism spectrum, has type 2 diabetes and is registered blind. “I do everything for her,” says Moon. On weekends when her daughter stays with her father, Moon worked part-time at Tesco earning £9.50 an hour. This would comfortably keep her under the earnings threshold of £127 a week at the time, especially when deducting allowances for fuel and pension payments – or so she thought. The Department for Work and Pensions (DWP) contacted Moon in 2019 to say she had breached the earnings limit and would need to pay back every penny – or she would be taken to court. Moon, terrified, contacted Citizens Advice for help. It analysed her payslips going back to July 2016, when she started work at Tesco, and found that – even on the strictest understanding of the DWP’s rules – she had exceeded the earnings limit by about £3 most of those weeks. Some weeks it was as little as 50p over. She appealed for clemency but the DWP refused to budge. It refused her offer to pay back the amount she was not entitled to – about £800 over the course of three and a half years. Instead, she would have to pay back every penny of carer’s allowance over that period – known as the DWP’s “cliff edge”. It amounted to £11,292.75 – plus an additional £50 civil penalty. “They’re heartless. They’re cold, they’re calculating,” says Moon, as dozens of unpaid carers came forward this week with similar stories of being pushed into hardship by the DWP’s actions. The DWP could and should have spotted Moon’s minor infraction almost as soon as she began work in July 2016, using its real-time data-matching technology. But it was not until three years later, when the overpayments had reached five figures, that the department contacted her: yet more proof that the DWP has failed to fix the problems laid bare by a report by MPs in 2019. There was another cruel twist for Moon. She reluctantly agreed to repay the £11,292 in full: the threat of a criminal record, and the possible implications for her daughter, were too terrifying to bear. Citizens Advice helped her work out what she could afford to repay each month given her outgoings. The most she could afford was £5, she said. But the DWP refused and ordered her to pay back £60 a month – meaning Moon will be 73 by the time it is paid off in 2035. “My guess is I will be paying that back for the rest of my days, and still doing a full-time caring job,” she says. The case highlights yet another flaw with carer’s allowance: single parents get no more help than a bigger family, despite them being vastly more reliant on the small weekly stipend because they have less ability to earn an income. Yet despite it all, Moon considers herself lucky. Her daughter, who the Guardian has chosen not to name, is “an angel”, she says, and although the little money they have makes life a struggle, they are not destitute. “It’s really sad, but it’s life. I wouldn’t change my life as it is, at all.” The DWP has been approached for comment.