A cascade of administrative failures in the Child Maintenance Service (CMS) has left thousands of British parents out of pocket by an average of £20,000, prompting the Department for Work and Pensions (DWP) to demand an urgent independent inquiry. The scale of the error, described by insiders as "industrial-level incompetence," has undermined trust in a system designed to support children after family separation.
Data obtained by the BBC reveal that over 15,000 cases have been miscalculated since 2018, with parents overpaying or underpaying by significant sums. In some instances, single mothers have been forced to rely on food banks after the CMS overestimated their income and demanded repayment of alleged overpayments. Meanwhile, non-resident parents have been billed for children they do not financially support due to outdated records.
The errors stem from a flawed computer algorithm, introduced in 2017, that was supposed to automate calculations based on tax data. Instead, it has repeatedly misapplied rules, failing to account for changes in employment, shared care arrangements, or disabilities. A whistleblower from within the CMS told the Guardian: "We knew the system was broken within months. We flagged it repeatedly, but managers were more concerned with hitting targets than getting the numbers right."
The DWP has confirmed that a total of £2.3 billion has been incorrectly assessed, with individual overpayments reaching £20,000 in extreme cases. The department has allocated £50 million for redress, but campaigners argue this is insufficient given the emotional and financial toll. "This is not just about money. It is about the state failing children," said Jane Harris, director of the charity Gingerbread. "Parents already navigating the trauma of separation are being crushed by a bureaucracy that cannot count."
The government has ordered a statutory inquiry, to be chaired by a High Court judge, with powers to recommend legal changes. DWP Secretary Mel Stride called the situation "unacceptable" and pledged that all affected parents will be reimbursed with interest. Critics, however, note that previous redress schemes for welfare errors have taken years to deliver.
From a systems perspective, the CMS failure mirrors challenges seen in other large-scale government IT projects: modular upgrades that fail to integrate with legacy databases, over-reliance on outdated rules-based logic, and insufficient real-world testing. The public is left shouldering the cost of digital incompetence.
For parents like Sarah, a 34-year-old mother of two in Manchester, the error has been devastating. "They told me I owed £18,000 because of a 'data mismatch.' I had to sell my car. When I proved they were wrong, they said it would take 18 months to fix. My children lost a year of stability because a computer could not subtract."
The inquiry will report within 12 months. For thousands of families, that will seem an eternity. The lesson, as always, is that algorithms are only as reliable as the people who program them. When those people fail, it is the most vulnerable who pay.
