What is an ERN (PAYE Reference Number) and why do I need it?

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An ERN (Employer Reference Number) is issued to every UK company that registers as an employer. It is also referred to as a PAYE reference number because it is used as a unique identifier by HMRC when processing payroll information like income tax and national insurance. An ERN is included in the welcome pack HMRC sends out to each newly registered employer.

Every business must register as an employer with HMRC as soon as it hires its first employee on Pay As You Earn (PAYE).

What does an ERN look like?

The employer reference number is in two parts. The first part is three digits, which identifies the HMRC office number that deals with the company’s PAYE (e.g. 135). The second part of the reference, which follows a forward slash, is the tax office’s reference for the employer itself. (e.g. AB56789). The letter or letters in the ERN should be entered in upper case.

A business registered as an employer before 2001 will have an employer reference number in the form 135/A56789. In 2001 an extra alphanumeric letter was added, therefore ERNs registered after that date will take the form 135/AB56789.

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A company's ERN displayed on a typical payslip
ERN Employer reference number PAYE reference

Who is ERN exempt?

The only ERN-exempt companies are those who do not operate a PAYE scheme because they:

  • have no employees
  • have employees who are all paid below the Lower Earnings Limit and none of whom has another job or is in receipt of a pension or benefits
  • are registered outside England, Wales, Scotland & Northern Ireland, e.g. Jersey, Guernsey & the Isle of Man

If you’re at all unsure whether these exceptions apply to your company, you should consult your accountant or HMRC directly.

When do I need my ERN?

  • When completing the annual PAYE return. HMRC won’t accept the submission without your ERN.
  • When an employee asks you for it to complete their tax credits or student loan application, for which it is required.
  • When taking out employer’s liability insurance, which it has been a legal obligation for employers to have since the Employers’ Liability (Compulsory Insurance) Act 1969. ERNs are recorded on a database run by the Employers’ Liability Tracing Office (ELTO), which exists to give employees easy access to their present and previous employers’ employers’ liability insurance data, even after years have passed since the employment ended. The aim is to ensure that claims are settled with the insurer which covered the company at the time rather than the employer.
  • In correspondence with HMRC about income tax and national insurance.
  • It should be quoted on most payslips, P60s, P11Ds and P45s.

Your ERN is not to be confused with your …

  • Accounts Office Reference (AORN), a unique series of thirteen characters used by HMRC to link an employer’s PAYE payments to their online PAYE account. It is issued alongside an employer’s ERN (PAYE reference). The two references are easily confused as they often appear together on P45s, P60s, P11Ds and payslips.
  • Company registration number (CRN), issued by Companies House on incorporation of every company. It consists of eight characters: eight digits or two letters followed by six digits. It is used when filing company records at Companies House and can be found, among other places, on your certificate of incorporation. Read more about your CRN
  • VAT number, issued by HMRC to companies who register for Value Added Tax. Consists of nine digits, sometimes with ‘GB’ added at the start.
  • Unique taxpayer reference (UTR), issued by HMRC to self-employed people and consisting of 10 digits. Used when dealing with affairs such as tax returns, tax refunds etc. In partnerships, each partner needs their own UTR. Read more about UTRs
  • Companies House authentication code, a 6-character alphanumeric code provided by Companies House upon registration. It acts as your electronic signature to allow you to access the WebFiling system and make changes to your company records. It will be something like A1BC2D. Read our article about this authentication code.

Where can I find my ERN?

You should be able to find your employer’s reference number in the following places:

  • In the Yellow Booklet supplied by HMRC in your welcome pack when you first registered as an employer
  • On any historic payslip, P45, P60 or P11D issued to past or present employees
  • Other correspondence from HMRC about PAYE
  • Your accountant or bookkeeper, if you outsource your payroll
  • As a last resort, you can call HMRC’s Employer Helpline on 0300 200 3200. While they can resend the reference to the employer, it may take up to two weeks to arrive.

If you don’t have any record of an employer reference number, it may be because you are not registered as an employer. That’s no problem if the business doesn’t employ anyone, but if it does, and they are paid above the PAYE tax threshold, it’s imperative that you register immediately with HMRC.


All companies are required to maintain up to date company records. Inform Direct is the perfect tool to help you easily keep everything up to date.


This article was originally published in 2015. In July 2022 it was thoroughly revised and updated.

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