What is an Employer Reference Number (ERN)? A small business guide

If you have employees, it’s likely your business will have an Employer Reference Number (ERN). 

It’s important to know your ERN number as you’ll use it frequently when completing payroll, filing tax returns, or buying employers’ liability insurance.

You may also need to provide your ERN to employees if they want to apply for Universal Credit or tax credits.

What is an Employer Reference Number?

An Employer Reference Number (ERN) is a unique number given to your business by HMRC when you register for Pay As You Earn (PAYE) – it’s also known as an employer PAYE reference number.

An ERN is a unique combination of letters and numbers, used by HMRC to identify a business for employment or tax purposes.

• Where can I find my PAYE reference number?
• Why and when do you need an ERN number?
• How to get an ERN in the UK
• Common ERN issues and how to resolve them
• How are Employer Reference Numbers used?
• Why do I need to give my ERN to my insurer?
• Employer Reference Numbers vs other HMRC identifiers
• What are the exceptions to PAYE?
• Employer Reference Number FAQs

Where can I find my PAYE reference number?

Employers can find their ERN in several places, such as:

• HMRC correspondence – when you first register as an employer with HMRC, you’ll receive a confirmation letter and welcome pack. Both of these will include your ERN, usually in the top right hand corner. It’s sometimes labelled as an ‘employer PAYE reference’
• employer forms – ERNs are included on forms such as P11Ds, P45s, and P60s
• payslips – your Employer Reference Number should appear on any payslip generated by your payroll software
• HMRC online account – you should also be able to find your PAYE reference number in your HMRC account and in emails from HMRC relating to PAYE

Why and when do you need an ERN number?

As an employer, you’ll need an ERN in several circumstances, such as filing paperwork for HMRC or on request of your employees.

Here are three common instances when you’ll need your Employer Reference Number: 

1. Payroll and tax – an Employer Reference Number is a requirement of registering with PAYE. You won’t be able to run payroll or submit end-of-year returns without one. An invalid or missing ERN is one of the most common reasons end-of-year returns are rejected
2. Employee documentation – your employees may ask you for the business’s ERN if they need to fill out a form for the Student Loans Company or apply for Universal Credit
3. Insurance – if you employ people, it’s a legal requirement to have employers’ liability insurance. Your insurer will ask for your ERN when buying this cover. This is a Financial Conduct Authority requirement and allows them to track your policy if you make a claim in the future

Remember, if you’ve registered as an employer with HMRC, it’s a legal requirement to have an ERN. If you run the business and pay yourself through PAYE, you’ll still need one.

How to get an ERN in the UK (Registering as an employer)

You get your PAYE reference number when you register as an employer with HMRC.

If you’re a limited company with up to nine directors, you can register as an employer online. You’ll need to answer questions about your business before signing in to your Government Gateway account to register.

For most other businesses, such as sole traders, partnerships, or companies that hire subcontractors under the Construction Industry Scheme (CIS), you may be able to register online. However, in some circumstances you may have to register by phone.

To get your PAYE reference number, you’ll need to register before your employee’s first payday (you can’t register more than two months in advance). You’ll be sent your ERN in a letter.

If you need to pay someone before you get your ERN, you can:

• run payroll
• store the full payment submission
• send a late full payment submission to HMRC

Common issues with ERN numbers and how to resolve them

An issue with an Employer Reference Number could cause problems for your business, either with HMRC or your employees.

What if I’ve lost my ERN number?

It’s important to keep hold of your employer PAYE reference number, as you’ll need it regularly throughout the tax year. If you lose it, you’ll be able to find it in letters or emails about PAYE from HMRC.

It’ll also appear on any P45s or P60s for previous or current employees.

If you don’t have any record of your ERN, it may be that you’re not registered as an employer. If this is the case, but you’re employing or intend to employ someone, you should register as soon as possible. Read our employment status guide to work out what applies to you.

Delayed or incorrect ERN

You may experience a delay in receiving your ERN from HMRC. Delays of five to 10 days are common, so you may just have to wait. 

If your delay is longer, you can check your employer registration application status on HMRC’s online portal. Alternatively, you can call HMRC’s PAYE helpline on 0300 200 3200.

If your ERN details are incorrect, you’ll need to contact HMRC with the correct information. Acting quickly can save future payroll issues. 

Confusion with Accounts Office reference number

Employers sometimes confuse Employer Reference Numbers with Accounts Office reference numbers.

The ERN identifies a business’s PAYE registration. On the other hand, an Accounts Office reference number tracks payments made to HMRC’s accounts office. 

Both are likely to appear on payslips and payment letters, so it’s important to understand and be able to distinguish the difference.

How are Employer Reference Numbers used?

As a business, you’ll use your Employer Reference Number in a different way to HMRC.

Employers commonly use ERNs for:

• payroll administration – your ERN will be included in every full payment submission you make, as well as on payslips
• employment history – if a claim is made against you, you may need to use ERNs to work out someone’s employment history
• employers’ liability insurance – you’ll need to provide your ERN when you buy this insurance

HMRC commonly uses ERNs for:

• tax collection – to identify your business when you pay income tax and National Insurance through PAYE
• linking PAYE schemes – if a business works out of different locations, or is merged or acquired by another business
• compliance monitoring – to track a business’s payroll and tax history

Employer Reference Numbers vs other HMRC identifiers

ERNs are sometimes confused with other HMRC numbers used in tax and payroll processes.

As well as the Accounts Office reference number, a unique taxpayer reference (UTR) number is also sometimes confused with an ERN. A UTR number is unrelated to PAYE and is used as part of the Self Assessment tax return process.

By understanding the differences between these numbers, employers can ensure a smooth payroll and ensure compliance with HMRC.

What are the exceptions to PAYE?

You won’t have an employer PAYE reference number if you don’t have to register under PAYE. You don’t have you register for PAYE if:

• your employees are paid as self-employed or paid via an agency
• no employee earns more than the lower earnings limit (£123 a week in 2024-25 and £125 a week in 2025-26)
• your employees are unpaid volunteers
• your business is based in the Channel Islands or the Isle of Man

Employer Reference Number FAQs

Where can I find the ERN number?

You can find your ERN number in correspondence from HMRC, on employer forms such as P11Ds and P45s, on payslips generated by your payroll software, and on your online HMRC account.

Is an ERN number the same as a PAYE number?

Yes, an Employer Reference Number is the same as a PAYE number. It’s also sometimes called an employer PAYE reference number.

What is an example of an ERN number?

Here’s an example of an Employer Reference Number – 123/A45678 or 123/AB45678.

An ERN is a unique combination of letters and numbers. It’s usually made up of two parts – a three-digit HMRC office number and a reference number for your business.

Can a business have more than one ERN?

Yes, a business can have more than one ERN. However, most small businesses will only have one. 

Reasons for having more than one ERN include larger businesses operating from different locations or businesses that have been acquired by or merged with another business.

If you have a Simply Business policy with us, please submit your employer PAYE reference number (ERN) if you haven’t already.

Useful guides for small businesses

• What is gardening leave? A guide for employers
• How to create an occupational health policy
• Self Assessment tax returns: a guide for the self-employed
• What does employers’ liability insurance cover?