The short version
HMRC says anyone who interacts with HMRC on behalf of others about their tax affairs, and is paid to do so, must register. That applies even if tax advice is not your main service or you only have one client. The legal entity registers, not each individual employee.
What counts as interacting with HMRC
HMRC lists contact by phone, post or email; messages through GOV.UK or the HMRC app; making payments; and sending returns, claims or other documents.
Registration windows
HMRC describes registration windows of three months, depending on your situation. Dates it currently lists:
- 18 August 2026: the window for firms with existing Self Assessment or Corporation Tax agent codes ended.
- 18 November 2026: third-party payroll service providers.
- 31 December 2026: financial services organisations.
Other new tax advisers are told to register now. Application-window dates are not the same as statutory appointed days; read the source and scope page for how this product treats dates.
Who HMRC says does not need to register
- In-house tax teams handling their own company’s affairs
- Free advisers, such as charities or people helping friends and family
- Professionals legally required to deal with HMRC, such as insolvency practitioners and pension firms
- VAT representatives, customs specialists and import duty representatives
- Software developers providing accounting or tax software
- Representatives in court or tribunal appeals
- People simply responding to HMRC information requests
If you do not register
HMRC says unregistered advisers cannot interact with HMRC for clients and may face sanctions.
Next steps
Work out whether your entity is in scope, then see the registration conditions and our internal preparation checklist.
Source: HMRC guidance, checked 9 October 2026. Official guidance can change; confirm against it before relying on a position. This is not tax or legal advice.