You can complete a secure online form to tell HM Revenue & Customs (HMRC) about customs or excise fraud or tax evasion. You don't have to give your name or address on the form, but letting HMRC have your details means they can make better and safer use of the information you give them.
If you send information to HMRC by using the online form your message is secure, but the email reply to you, which will be sent over the internet, is not. Information sent by email over the internet is not secure and is at risk of being read by people other than those it was intended for. If you have provided your details, HMRC will reply to you by telephone or letter if their reply contains personal or sensitive information.
If you have any doubt about the authenticity of an email you receive which claims to have come from HMRC please do not follow any links within the email, disclose any personal details or respond to it.