A warning has been made by HM Revenue and Customs to millions of people who will be filling in Self Assessment forms to be aware of fraudsters in the lead-up to the January 31 filing deadline.

Over the last year, HMRC received nearly 900,000 reports from the public about suspicious HMRC contact made by phone calls, texts or emails.

More than 100,000 of these were phone scams, while in excess of 620,000 reports from the public were about bogus tax rebates.

Some of the most common techniques fraudsters use include phoning taxpayers offering a fake tax refund.

Others include pretending to be HMRC by texting or emailing a link which will take customers to a false page, where their bank details and money will be stolen.

Fraudsters are also known to threaten victims with arrest or imprisonment if a bogus tax bill is not paid immediately.

HMRC operates a dedicated Customer Protection team to identify and close down scams but is advising customers to recognise the signs to avoid becoming victims themselves.

Genuine organisations like HMRC and banks will never contact customers asking for their PIN, password or bank details.

Customers should never give out private information, reply to text messages, download attachments or click on links in texts or emails which they are not expecting.

Customers are urged to take action by forwarding details of suspicious calls or emails claiming to be from HMRC to phishing@hmrc.gov.uk and texts to 60599.

Customers who have suffered financial loss should contact Action Fraud on 0300 123 2040.

Tax is automatically deducted from most UK taxpayers' wages, pensions or savings. Where tax is not automatically deducted, or when people or businesses have earned additional untaxed income, they are required to complete a Self Assessment tax return each year.

People need to complete a tax return if they:

• earned more than £2,500 from renting out property
• Their partner received Child Benefit and either of them had an annual income of more than £50,000
• received more than £2,500 in other untaxed income, for example from tips or commission
• are self-employed sole traders
• are employees claiming expenses in excess of £2,500
• have an annual income over £100,000
• earned income from abroad that they need to pay tax on