You may receive an email from someone who claims to be from your bank or some other well known and trusted organisation such as HMRC or even your favourite supermarket. The email will look official and will include signage from the organisation they are claiming to be. This type of email scam is known as phishing.
If the sender is claiming to be your bank, the email will state that there has been a problem with your account and then direct you to a fake website which looks the same as the genuine one. You will then be asked to enter your bank account details and password to log into the fake website. The scammer will then use your password and account details to steal all the money from your bank account.
Alternatively the sender may claim to be from the HMRC and advise you are due a tax return. You will be directed to a website which looks the same as the genuine HMRC website and then you will be asked to enter your bank account details and password in order to receive your tax return. The scammers will then use your details to steal all the money from your account. In addition, sometimes the scammer will ask you to call a premium rate number first, meaning, on top of the money they steal from your bank, you will receive a large phone bill from the telephone call.
Another very common type of phishing scam is when the sender claims that you have been chosen to receive a cash voucher for a major supermarket chain. The voucher can be of any value but is usually around £500. You will be advised to call a premium rate telephone number to claim the voucher. The voucher will not exist and you will be left with a large telephone bill. There are many variations of this scam and sometimes you may be directed to a website first and asked to enter bank details to claim the voucher, the scammer will then use your bank details to steal all the money from your account.
Organisations such as banks or the HMRC will never contact you by email or telephone.