In 2005/06 HM Revenue and Customs (HMRC) prevented payments of over £400m in respect of suspected organised fraud, according to a new report from the National Audit Office (NAO). HMRC estimates however, that it overpaid £1.8bn and underpaid £556m in tax credits in 2004/05 and the position for 2005/06 is expected to be similar. NAO…