[1] Every organisation operating a Pay As You Earn (PAYE) scheme is allocated an ERN, a unique set of letters and numbers used by HMRC (and others) to identify each employer, consisting of a three-digit HMRC office number and a reference number unique to each business.
[2] The ERN is alphanumeric (consisting of both letters and numbers) in the format of 123/XX12345, or 123/X12345 (prior to 2001), where the first three characters represent the Tax Office catchment area and the last six or seven characters represent a unique organisation or employer.
The ERN can be found on mandatory HMRC documentation, including P45, P60, P11/D and payslips.
[4] ERN's are also used by the Employers' Liability Tracing Office, an independent industry body recognised by the FCA,[3] who can assist employees to find their former employer's Employers' Liability Insurance provider if they need to make a claim for injury or illness incurred at work.
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