Working as a Tax Agent: what you need to know

HMRC Accounts for Tax Agents - an Introduction

The process for accessing HMRC services as an agent is undergoing some considerable change. As a tax agent you will  need to have one or both of two online accounts with HMRC - an Agent Online Services Account (AOSA) and/or an Agent Services Account (ASA). The AOSA is used for all HMRC returns that are not Making Tax Digital (MTD) based, whilst the ASA is the one that covers MTD.

You may also need to obtain a tax agent code (depending on which tax service you wish to offer) and you will need to ensure that each one of your clients authorises you to act on their behalf for each service you carry out for them.

In April 2021 a process commenced to ensure all VAT returns were migrated over from HMRC’s mainframe system to its Enterprise Tax Management Platform (ETMP). If you are submitting VAT returns via the Government Gateway you will now do this through your ASA – the figures will be uploaded as normal but the screen might look different. When the migration starts Agents won’t know whether their client has been migrated or not. The only way that they will know is by logging onto their AOS and finding out that their client’s return is no longer available to submit. They then need to log into their ASA to submit for their client via a link on the “View and Change” screen. This process will be seamless as long as you have already created your ASA and copied over your VAT clients to that account (Don’t forget that you can copy over your client relationships to your ASA and still act for your clients for VAT in your AOS).

From November 2022 the 'old' system has closed and trying to upload VAT returns via this method will now return an error.

From April 2024, MTD for self-assessment will commence with quarterly uploads and access to this will also be via the ASA account.

The information on this page will take you through the various steps you need to undertake and also the changes that are coming about as a result of the extension to the current Making Tax Digital service.

Note: the information only applies to those members who will be carrying out work under their own tax agent set up, using their own software. If a member is using software at a client's premises, using the client's HMRC access, then the following does not apply but you must be careful that you do not actually use their authorisation codes yourself as  these are specific to the account holder and should not be divulged.

The links below will take you to the relevant sections on this page. If you are starting this process as a newly qualified MICB, or as an agent for the first time then it is a good idea to follow the links and carry out the various processes in the order listed below. You may already have some of these in place already in which case simply fast track to the section you need to add or review.


Qualifying to offer services as a tax agent through ICB

Agent Online Services Account (AOSA)

Agent Services Account (ASA)

Obtaining Tax Agent Codes

Adding services to your agent account

Removing services from your agent account

Adding other users

Client Authorisation

Change or cancel authorisations as an agent

Changing your own agent details with HMRC



Qualifying to offer services as a tax agent through ICB


As a member of ICB, wishing to offer tax agent services, you must be qualified in the tax area you wish to offer and have a practice  licence with ICB. A practice licence through ICB covers you for the relevant Anti-Money Laundering Supervision required by law for all practising bookkeepers and accountants.

The qualifications you will need to have successfully passed (or been exempt) for the relevant service you wish to offer are as follows:

VAT - Must have passed or been exempt from the relevant membership qualification and be using the designatory letters MICB

PAYE - Must have passed or been exempt from the relevant payroll qualification and be using the designatory letters PM Dip

Self-Assessment - must have passed or been exempt from the Level 3 Certificate in Self-Assessment and/or the Level 4 Diploma in Self-Assessment

Corporation tax - must have passed or been exempt from the Level 4 Diploma in Financial Statements and the Level 4 Diploma in Corporation Tax



Agent Online Services Account (AOSA)


You will need to register for this account if you wish to offer the following services to your clients: PAYE; CIS; Self-assessment and Corporation Tax. Note all VAT submissions are now accessed via the Agenet Services Account. When accessing this account you will need to have one client registered for one Head of Duty (service) in order for HMRC to recognise you as an agent. Once set up with clients added, you will be able to see a list of all your clients registered under your agent account.

In order to set up your account you can use this link. Note: this link may well take you to an error page in which case follow the log in link they give you for the Government Gateway and continue from there!

You will firstly have to give an email address to enable you to receive a recognition code (sent to that email address). You should really use the business email address for your practice. Once you receive and enter this code you will be asked to provide your full name after which you will set up a password. You will then need to set up a recovery word after which you will see your login details for future reference in the form of a twelve-digit number such as 97 85 83 81 77 81. You will then receive your agent ID in the format


Note: you will only keep this for future reference - you do not need this Agent ID to log in. It will however appear on your agent page the next time you log in.

In order to access this account again you can search for 'Login' from's home page and enter your 12-digit reference number and the password you set up. 

You will now be taken to your main Agent page from which you can start to add the services you wish to offer (explained in 'Adding services to your agent account').

Before HMRC recognises you as an agent you will need to add one Head of Service (e.g. VAT or PAYE) and register one client under that service onto your AOSA.

If you are adding Self assessment or Corporation Tax you will need to have obtained, or obtain, a relevant Agent Code (explained in 'Obtaining Agent Tax Codes').

The first person to be set up on an account will automatically be set up as an 'administrator'. Other individuals may be added on as additional users (see the section Add a user)

Agent Services Account (ASA)


This is the service that is accessed and used by agents that are submitting VAT Returns.  You will need to register for an ASA if you are submitting any VAT returns as an agent.

Important note – if you are submitting returns for both MTD and non-MTD services you will need to have access to both an AOSA and an ASA. If you are only completing returns under MTD then you do not need to have an AOSA.

The main link to the relevant page can be found here

If you do not already have an AOSA (or are only offering MTD services) then, to start the process, the easiest way to register is to apply in writing and supply details of your business and membership of ICB. The postal address that you need for this application is:

Central Agent Maintainer Team
National Insurance Contributions and Employer Office
HM Revenue and Customs
United Kingdom

HMRC will not register you if you do not give the correct information, or they are not satisfied with the information provided.

Once this application process is completed HMRC adds your UTR to an ‘Allow List’ which then enables you to register for Agent Services and bypasses the checks that look for an existing registration and client. HMRC will tell you if you are registered within 28 days.

Once you have received that confirmation from HMRC, you can access the screen again and click on the link to ‘Create Agent Services Account’. Clicking on ‘Create Now’ will take you to a log in screen. ‘Create Sign in details’ (underneath the main ‘Sign In’ section which should not be accessed at this stage), follow through the various questions and HMRC will bypass the normal client requests that you would need for creating the AOSA.

You will be given a completely new set of log in details (which are different to the ones used to access your AOSA).

Note: you may still apply for an ASA (without writing in) by simply clicking on the Create Agent Services Account and following the online form through, but at some stage you will need to have additional informaton including an authorisation code from a client. The process will be delayed if you cannot provide this information. If you have previously applied in writing and been approved by HMRC then you may proceed to finalise the setting up of your account with no further delays.

Once you have added clients to your ASA, note that at present you will not be able to see a list of clients that are registered under this account (as you can in the AOSA) but as the number of services are added to the system then HMRC are hoping to bring in this availability.

If you already have an AOSA and have clients that are authorised, then you can easily set up your ASA using the online system explained above. You can then migrate your clients across as you need to.  If you have an AOSA but have no authorised clients, the simplest process is to wait until you have a client that you can have authorised and listed in your account, then set up your ASA online and move your client across.


Obtaining Tax Agent Codes


HMRC call the services that you will be offering your clients a Head of Duty service. In order to offer services covering PAYE, CIS, Self-Assessment or Corporation Tax you will need to obtain a separate Agent Code for each service. For VAT you will either need to be VAT registered yourself or, if not, you will need to obtain a VAT Agent Reference Number. Below is an explanation of how to obtain the various codes or reference numbers you might need.

To obtain an agent code for Self-assessment or Corporation Tax you will need to either have an Agent Online Services Account set up (in which case you can apply online), or, if not, you will need to apply in writing, with relevant business and practice licence details, to

HM Revenue and Customs - Central Agent Authorisation Team
Benton Park View
NE98 1ZZ
United Kingdom

To obtain an agent code for PAYE and CIS you can apply online.

For VAT services, if you are VAT registered you will need to use your VAT number to set up agent authorisation for offering VAT services.

If you are not VAT-registered, you’ll need to apply for a VAT agent reference number (which can be done online) before you can set up authorisation.


Adding services to your agent account


Once  your agent account/accounts is/are set up you will need to start adding the services to the relevant account. Log into the relevant account and view the 'Services you can add' box. Choose from the list that appears and follow the links.


Removing services from your agent account


Once logged in there is also a link to enable you to remove services you no longer wish to offer.


Adding other users

This section is awaiting an update from HMRC


Client Authorisation


If you act as a tax agent or adviser, you must have formal authorisation to deal with HMRC on your client’s behalf.

You and your client can set up the authorisation securely online. Depending on the type of service you will need to do this either through your AOSA or your ASA.

Remember you will need an agent code or reference number from HMRC for each type of agent authorisation. Make sure you have this before you start to set up authorisation online.

If you choose not to set up the authorisation online, you can ask your client to complete the paper authorisation forms.


Change or cancel authorisations as an agent

Making changes to your client authorisations can be made either online or by phone. 

You can use your HMRC online services account to:

  • manage your client lists - view, download or update
  • remove a client that you no longer act for - you will need to do this separately for each online service
  • update your contact details - for example, your firm’s email address or phone number

Once you remove a client from your online account, you will not have access to any of their data. Make sure you take copies of anything you have submitted online for that client before you remove them from your client list.

You can call the Agent Dedicated Line to let HMRC know:

  • you no longer act for a client
  • about changes to some client details

You will be asked some security questions to check your identity and you will need to provide your client’s name and reference number, for example, National Insurance number or Unique Taxpayer Reference (UTR).



Changing your own agent details with HMRC

Notification of a change of address for a tax agent can sometimes be made online but you may need to write to the Central Agent Authorisation Team to tell HMRC about changes to your:

  • business name
  • business address
  • trading status as an agent - for example, if you stop trading as an agent or your firm merges with another agent

If you stop trading as an agent HMRC will cancel any agent codes or reference numbers you have. You will need to apply for new ones if you start trading as an agent again.

Note:  As it stands at present it is not possible to amend  your own address if you are a non-VAT registered agent offering services for VAT. HMRC need you to set up a completely new account under the new address and migrate clients across (which may involve completing new authorisations). ICB are currently lobbying for this to be changed as soon as possible.