I always knew that that the tax credit system was in a bit of mess, but I have to admit I was staggered to learn that the cost of just handling complaints is over £6 million each year. It seems the Treasury don't actually know the exact figure, but the Treasury minister, Jane Kennedy, said in Parliament that the "cost of dealing with complaints in the Tax Credit Office between 1 November 2006 and 31 October 2007 was around £6.5 million".
If you're wondering why it's not an exact figure that is because "it is not possible to provide costs for other areas of HMRC that might also handle complaints relating to tax credits". So basically the Treasury thinks it might be even more. That's an incompetent system, and incompetent accounting of how much the mess is costing all thrown into one!