ICAEW.com works better with JavaScript enabled.

Agent reference number checks paused until November

Author: ICAEW Insights

Published: 02 Oct 2026

Contents
HMRC says that, from 18 November 2026, it will resume asking some firms to provide their agent reference number (ARN) when they contact HMRC, having announced a pause on such requests to give firms more time to prepare.

Background 

In December 2023, HMRC announced that it would begin to use the ARN "as a key piece of information in connecting agent firms with their submissions to HMRC".  As a result of this, HMRC said that agents should expect to have to provide their ARN more often as part of their "regular contact and transactions with HMRC".  Over time, this has been built into some agent processes and forms.  

What is an ARN? 

First introduced in 2017, the ARN is an 11-character reference made up of four letters, including ‘ARN’, followed by seven digits, for example: XARN1234567. The ARN can be found on the firm’s agent services account (ASA) homepage. A firm may have more than one ARN.  

Current situation 

Since 18 August 2026, firms using telephone or webchat to contact HMRC may have been asked to provide their ARN in order for HMRC to check whether the firm had registered for an agent services account (ASA) as part of the roll out of mandatory registration with HMRC. This is referred to here as an ‘ARN check’.    

However, HMRC has now announced in its stakeholder digest email that it has paused ARN checks to allow firms more time to prepare for this change in HMRC's processes. HMRC says that firms may still be asked for their ARN in other situations and that existing security, identity and client-authorisation checks will continue as normal. 

ARN checks will resume from 18 November 2026 for businesses that are required to register with HMRC as tax advisers. HMRC recommends that firms ensure that all relevant employees who interact with HMRC are aware of the firm's ARN from this date. An earlier article explains the timetable for firms that are required to register with HMRC as a tax adviser.

Prepare for 2026/27 series

ICAEW's Tax Faculty looks at the key tax changes applying from April 2026.

Further support on tax.
The Tax Faculty

ICAEW's Tax Faculty is recognised internationally as a leading authority and source of expertise on taxation. The faculty is the voice of tax for ICAEW, responsible for all submissions to the tax authorities. Join the Faculty for expert guidance and support enabling you to provide the best advice on tax to your clients or business.

  1. Final roll-out of multi-factor authentication gathers pace
  2. Agent reference number checks paused until November
  3. Review the roll-out of MTD, says ICAEW
  4. New tax relief needed for predevelopment costs, says ICAEW
  5. Tax news in brief 30 September 2026
  1. Why tax complexity matters
  2. New tax requirements for companies and directors
  3. How to prepare for a VAT enquiry
  4. Modernising and mandating agent registration
  5. Making sure a tax return is correct and complete

Further resources

Latest news
Making tax digital image
TAXwire and Tax Track

Stay up to date with the latest developments by signing up to the Tax Faculty's weekly enewsletter and listening to the Tax Track podcast series.

Listen now Newsletter sign up
  • Free
Practical guidance
Find out more about the Tax Faculty
Tax Faculty resources

The Tax Faculty offers expert guidance and support enabling you to provide the best advice on tax legislation to your clients or business. We offer clear direction in taxing times. Membership is open to everyone.

ICAEW support
Training and events

Browse upcoming and on-demand ICAEW events and webinars focused on developments in tax practice and policy.

Events and webinars CPD courses and more
Open AddCPD icon