Everything you need to know about Form 64-8

What is Form 64-8?

HMRC Form 64-8, Authorising Your Agent, is the official document a taxpayer (individual or business) signs to authorise an accountant, tax adviser, or other agent to deal with HMRC on their behalf. Once submitted and processed, HMRC will correspond with the agent — answering queries, sending notices, receiving information — for the tax regimes selected on the form. Most accountancy and tax adviser relationships in the UK start with a signed 64-8 covering the relevant taxes.

What 64-8 covers

The form has tick-boxes for each tax regime the authorisation should cover: Self Assessment (individuals or partnerships); PAYE (employers); VAT; Corporation Tax; Construction Industry Scheme; trusts and estates; tax credits; and High Income Child Benefit Charge. The taxpayer can authorise the agent for one regime or several. Authorisation continues until the taxpayer or agent ends it — usually through HMRC's online services or a new 64-8 designating a different agent.

When 64-8 is needed vs. online agent authorisation

HMRC has gradually moved most agent authorisation online through the Agent Services Account (ASA) and the digital handshake process — for many services, the taxpayer simply confirms authorisation in their HMRC online account. Form 64-8 remains the fallback for clients without digital access, for older regimes not yet fully digitised, and for cases where the agent prefers a written authorisation on file. Many practices use the digital route for new clients and 64-8 for the rest.

How to complete and submit?

The taxpayer completes their personal/business details, the agent provides their name and agent reference numbers, and both sign and date. Tick every regime the authorisation should cover. Send the completed 64-8 to the address listed in the form's instructions — HMRC has different central addresses for individuals, agents, and certain tax regimes. Processing typically takes several weeks, after which the agent appears on HMRC's records for the listed regimes. Keep a copy of the signed form for your records and update it when the agent changes or the authorisation ends.