Form 64-8, Authorising your agent, is the HMRC paper form you sign to let a paid agent, such as an accountant or tax adviser, deal with HMRC for you. It covers Self Assessment, PAYE, Corporation Tax, VAT, CIS, tax credits and more. HMRC prefers online authorisation, so the 64-8 is mainly for when that isn't possible, and you stay legally responsible for your own tax either way.
The details below come from HMRC's guidance on GOV.UK, as of October 2026.
What the 64-8 covers
One 64-8 can cover more than one tax. Your client, or you, if you're the taxpayer, can authorise an agent for:
| Tax | What the agent can do once authorised |
|---|---|
| Self Assessment | Submit returns, claim reliefs, discuss current and past returns, change details, give bank details for repayments |
| PAYE for individuals | See past employers, taxable benefits such as company car and medical insurance, pensions and PAYE dates |
| PAYE for employers | Access employees' personal and financial information |
| Corporation Tax | Access company and financial information, update contact details |
| VAT | Discuss VAT, sign paper documents, view and change details, appeal penalties |
| Tax credits | Act on the claim, but not receive payments |
| CIS | Note it on the form or in a letter to include Construction Industry Scheme |
When to use the paper form
HMRC says it's easiest to set up authorisation online through HMRC Online Services, and you can authorise an agent for a specific tax year using an online service or your business tax account. The 64-8 is the fallback if you can't use those. There are two exceptions where paper is the only route:
- Tax credits: you can't set up tax credits authorisation online, so a 64-8 is needed. Joint claimants must both sign the same form.
- High Income Child Benefit Charge information requests use a separate form, CH995.
For trusts, it's the other way round: a 64-8 won't give the agent access to the trust online service. Use the trust registration service to authorise the agent instead.
How to fill it in
- Download the current 64-8 form from GOV.UK. It's a 3 page PDF.
- Open it in the latest free version of Adobe Reader, then fill it in on screen and print it, or print it and fill it in by hand.
- Type or write clearly, and only inside the boxes.
- Enter the agent's correct agent code for each tax, for example a 6 character Self Assessment agent code in the Agent code (SA) box.
- Don't strike through unused boxes or add extra information in the fields.
- Sign, date and post it to the address on the form.
Don't add a covering letter unless it contains information HMRC needs to process the form. If you're registering for Self Assessment for the first time, register before sending the 64-8.
Where to send it
Most 64-8 forms go to HMRC's Central Agent Authorisation Team, but some go elsewhere:
| Authorisation for | Send it to |
|---|---|
| Most taxes | Central Agent Authorisation Team |
| Corporation Tax only | The HMRC office that deals with the company's Corporation Tax |
| A charity | The Charities Correspondence Team |
| A trust's tax affairs | The Trusts and Estates Team |
| An R40 repayment claim | HMRC, with the R40 |
| A client dealt with by the High Net Worth Unit | The High Net Worth Unit |
If HMRC has asked for the form to go to a specific office, send it there. Don't send a tax credits 64-8 with a tax credits claim form: claim forms go to the Tax Credit Office separately.
The change many people haven't caught
HMRC no longer accepts the 64-8 for limited authorisation, where you want an agent to help with one specific area of your tax but not act as your full agent on HMRC's records. For that, you write to HMRC instead. The letter needs your name and address, your tax reference such as your UTR, the agent's name and address, and your signature. An agent with limited authorisation can talk to HMRC and help with forms, but can't access your tax online.
For an HMRC compliance check there's a different form again: COMP1a, a temporary authorisation for HMRC to deal with your tax adviser.
Estates and personal representatives
A personal representative can use a 64-8 to authorise an agent to deal with a deceased person's estate for individual PAYE, Self Assessment and National Insurance. The personal representative signs, dates and adds their name and address, and enters the deceased person's National Insurance number or UTR in the relevant section.
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A tip for agents
If you're the agent, don't use your client's HMRC sign in details or log in to their tax account. HMRC also points out a trap: the digital handshake for the Income Record Viewer only lets you view income data. It doesn't authorise you to speak to HMRC for the client, so you still need a 64-8 or Online Agent Authorisation for that. Clients who are digitally excluded can be passed to HMRC's Extra Support Team, who talk them through authorising you by phone.
What authorisation doesn't change
Being authorised doesn't move any of your legal obligations to the agent. If your agent submits your tax return, you still have to check the information and tell them it's correct before it's sent. Keep your UTR to hand and watch the Self Assessment deadline yourself. If you want to switch or remove an agent later, HMRC lets you change or remove authorisation.
The verdict
Try online authorisation first, because it's quicker. Use the 64-8 when online isn't possible, and always for tax credits. Fill it in with the agent's correct codes, keep it inside the boxes, send it to the right team, and write a letter instead if you only want limited help.
Frequently asked questions
What is a 64-8 form?
HMRC's Authorising your agent form, which lets a paid agent such as an accountant deal with HMRC on your behalf for one or more taxes.
Where do I send a 64-8 form?
Usually to HMRC's Central Agent Authorisation Team. Corporation Tax only, charity, trust, R40 and High Net Worth Unit cases go to the teams listed in HMRC's guidance.
Can I authorise an agent online instead of using a 64-8?
Yes, HMRC says online is easiest. The 64-8 is for when you can't use the online services, and it's required for tax credits.
Can I use a 64-8 for limited authorisation?
No. HMRC no longer accepts the 64-8 for limited authorisation. You write to HMRC with a letter of authority instead.
Does a 64-8 make my agent responsible for my tax?
No. You remain legally responsible for your own tax and must check returns before your agent submits them.
