The HMRC CWF1 form is a form used by the UK's Her Majesty's Revenue and Customs (HMRC) to claim a tax refund for workers who have paid too much tax through their employment. The form is typically used by people who have had multiple jobs or whose income has changed during the tax year, resulting in them paying too much tax through the Pay As You Earn (PAYE) system. The form can be found on the HMRC website and must be completed and submitted with the appropriate documentation to claim a refund.