31 July is the date by which HMRC needs to receive your Tax Credit record update. You should have received your Renewal Pack by the end of June latest (if you haven’t, call 0845 300 3900). HMRC needs the renewal to check for any changes to your circumstances. Remember to read the instructions very carefully and send off before the deadline otherwise you may run the risk of Tax Credit payments being interrupted, or worse, being asked to return some of the money paid since 6 April 2007 plus any amounts overpaid for the previous year.
If you were awarded more than one tax credit award during the 2006-7 period, you need the equivalent number of Renewal Packs.
More details on how to renew your tax credit information at the HMRC website.