Small Business Accounting

What is My Accounts Office Reference Number (AORN)

By

Chris Andreou

accounts office reference number

Accounts Office Reference Number (AORN)

You can locate your Accounts Office Reference number (AORN) on the confirmation letter you receive from HMRC when you first register as an employer. The AORN contains 13 characters, and follows the format 123PA12345678.

After setting up a business in the UK, when a business registers as an employer or sets up Pay As You Earn (PAYE), HMRC issues Accounts Office Reference Number (AORN) and Employer PAYE Reference (ERN). These are the unique identifiers HMRC uses to identity employers and their PAYE transactions.

You can locate your Accounts Office Reference number (AORN) on the confirmation letter you receive from HMRC when you first register as an employer. The AORN contains 13 characters, and follows the format 123PA12345678.

After setting up a business in the UK, when a business registers as an employer or sets up Pay As You Earn (PAYE), HMRC issues Accounts Office Reference Number (AORN) and Employer PAYE Reference (ERN). These are the unique identifiers HMRC uses to identity employers and their PAYE transactions.

What is an Accounts Office Reference Number?

An Accounts Office Reference number (AOR) is a unique number issued by HMRC and is the reference used by an Employer when making payments to HMRC. It is a 13 characters number sent to you within approximately 5 business days by HMRC after business registration, along with a welcome pack for new employers.

It is also referred as Accounts Office Reference or PAYE Accounts Office Reference.

Accounts Office Reference Number Format

The format of an Accounts Office Reference is as below:

The total length of AORN is 13 characters which is sometimes extended to 17 characters to include ‘YYMM’ at the end for payments made by an employer relating to a specific period.

  • First 3 characters are numeric
  • 4th character is always ‘P’
  • 5th character is an alpha character
  • characters 6-12 are numeric
  • character 13 can be numeric or ‘X’

Accounts Office Reference Number Example

Some examples of accounts office references are:

  • 123PA12345678
  • 123PA1234567X
  • 123PA123456781511

The additional 4 digits you add to your 13-character accounts office reference number depend on whether you pay:

  • monthly
  • quarterly
  • annually

For example, if you pay PAYE tax monthly, additional 4 digits would be added as:

  • the last 2 numbers of the tax year your payment is for
  • the number of the month of the tax year your payment is for

So let's consider you are paying PAYE tax for the month of 6 July to 5 August 2023, the 4 numbers you need to add to the end of your accounts office reference number are 2304. This is worked out as follows:

  • the tax year you’re paying for ends in 2023 = 23
  • the month you’re paying for (6 July to 5 August 2023) is the forth month of the 2023 to 2023 tax year = 04

Learn about how to work out the extra numbers with examples here.

How to Find Your Accounts Office Reference Number

When you register your business with HMRC, they will issue you with an Accounts Office Reference number. This number will be sent to you in the post, usually within 5 business days of registering your business.

You can find Accounts Office Reference number on:

  • The letter you received from HMRC when you initially registered as an employer
  • The cover of your payment booklet
  • Emails from HMRC
  • PAYE bills

How Do I Find My Accounts Office Reference Number Online?


If you have already registered your business with HMRC, you can find your Accounts Office Reference number online through the HMRC website. You will need to log in to your HMRC account and click on the ‘My Business’ tab. Here, you will find your Accounts Office Reference number listed.

Alternatively, you can contact HMRC directly and ask them for your Accounts Office Reference number.

Use HMRC accounts office reference number checker to check the validity of the Accounts Office reference: Simply enter the accounts office reference number into the box (step 1) and click ‘Check reference’ (step 4) – there is no need to complete the other fields in order to check a reference.

When Do I Need My Accounts Office Reference?

You need to use your Accounts Office Reference:

  • When making any PAYE payments to HMRC including Income Tax, employees’ National Insurance, student loan repayments, Apprenticeship Levy payments, Construction Industry Scheme (CIS) deductions, and your employer’s Class 1 National Insurance contributions.
  • When contacting HMRC to discuss your PAYE payments or anything else related to your employer registration.

Why is an Accounts Office Reference Number Important?

Your Accounts Office Reference number is an important part of the process of setting up a business in the UK. It is used to identify your business in the eyes of HMRC and is used for any communication between you and HMRC. This number is also used to identify your business for tax purposes.

It is important to keep your Accounts Office Reference number safe and secure, as it is used to identify your business. If you lose or forget your number, you can contact HMRC and ask them for a new one.

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