Not Received Your Tax Rebate Cheque?
If the answers yes then it could be because you have moved house and not told HMRC.
If you have changed circumstances its best to let HMRC know as soon as possible. If you have moved house or got married letting HMRC know will make sure you receive all your post which could include a tax rebate cheque or notice of coding.
You can update your address with HMRC through your personal tax account of by using HMRC online services.