HMRC has issued a tweet to remind people how to find a lost National Insurance number. Anyone who has lost or forgotten their National Insurance number should first try and locate the number on paperwork such as their tax return, payslip or P60. If the National Insurance number still cannot be located a request can be submitted to HMRC using form CA5403. The completed form needs to be mailed to HMRC.

Alternatively, it is also possible to phone the National Insurance numbers' helpline to request details of the number. However, HMRC will not disclose the number over the telephone and will instead send the details by post. HMRC automatically sends a letter to teenagers just before their 16th birthday detailing their National Insurance number. These letters should be kept in a safe place.

HMRC is unable to assist with requests for new National Insurance numbers which should be requested from the JobCentre Plus - National Insurance number allocation service. An individual must have the right to work or study in the UK in order to apply for a National Insurance number.