To ensure that limited civil service resource is spent where it is needed ie advising, processing and making payments for those who should be benefiting from them in taking the step back into work.
Despite the fact my youngest child is now 22 years I regularly continue to receive an Annual Tax Credit Review pack and statement requiring postage costs for an A4 envelope informing me that I have a nil entitlement despite informing HMRC that my circumstances have not and are not likley to change
When I did receive tax credits it was generally for an incorrect amount and despite informing HMRC I eventually ended up making repayments for a year
It is also extremely difficult to actually speak to an Adviser using the 0845 telephone number and the recorded message asking you to continually ring back is frustrating . In all probability the lines are busy with people trying to get issues such as the above sorted diverting resources from being spent advising, processing and making payments for those who should be benefiting from them in taking the step back into work.