How Agents Get MTD Client Authorisation from HMRC
Step by step: how an accountant requests authority to act for a client under MTD, the proof-of-knowledge check, how the client accepts, invitation statuses, and de-authorising a client.
The short answer
To act for a client under MTD, an agent sends an authorisation request through their Agent Services Account, entering the client's details (name, National Insurance number, postcode) as a proof-of-knowledge check. HMRC invites the client, who accepts once via their own Government Gateway. After acceptance, the agent's own credentials cover that client indefinitely, with no repeated client login.
Before you can file for a client under MTD, HMRC needs the client to authorise you. Here's exactly how that flow works for agents.
The one-time authorisation flow
- You send a request through your Agent Services Account (usually from within your software's "Add Client" step).
- You enter the client's details as a proof-of-knowledge check — typically name, National Insurance number and postcode (or VAT number and registration date for VAT).
- HMRC issues an invitation to the client.
- The client signs into their own Government Gateway once and accepts.
- From then on, your own credentials cover that client — no repeated client login for each submission.
The proof-of-knowledge check
The client details you enter aren't just data capture — they're HMRC's way of confirming you genuinely know the client before it lets an invitation go out. Get them from the client directly and double-check them; a mismatch blocks the invitation.
The first client vs later clients
The very first client acceptance also triggers a one-time broader agent authority grant for your firm. Subsequent clients don't repeat that step — they just accept their individual invitation.
Main vs supporting agent
HMRC lets an agent act in a main or supporting role. The difference affects what you can view and change, so choose the right role when you set up the relationship and check HMRC's guidance if you're unsure.
Tracking status — and cancelling
Every invitation has a status:
| Status | Meaning |
|---|---|
| Invited | Sent, awaiting the client's acceptance |
| Accepted | You can now act for the client |
| Rejected | The client declined — you'll need to resolve and resend |
You can de-authorise a client, and clients can cancel your authority or reject the invite. Software that surfaces these statuses clearly saves a lot of "did they accept yet?" chasing.
ThisQuarter handles this end to end: enter the client's proof-of-knowledge details, send the invitation, watch the status, and once accepted, file that client's updates and final declaration under your agent credentials.
Key takeaways
- You request authority via your ASA using a proof-of-knowledge check.
- The client accepts once via their own Government Gateway — then no repeat logins.
- The first client triggers a one-time broader grant; later clients don't.
- Track Invited / Accepted / Rejected, and you can de-authorise anytime.
This article is general information, not tax advice. Check HMRC's agent authorisation guidance at gov.uk.
Frequently asked questions
How does a client authorise their accountant for MTD?
The agent sends an authorisation request through their Agent Services Account, providing client details as a proof-of-knowledge check. HMRC then invites the client, who signs into their own Government Gateway once and accepts. From then on the agent can act without the client logging in again.
What details does the agent need?
Typically the client's name, National Insurance number and postcode (or VAT details for VAT). These act as HMRC's proof that the agent genuinely knows the client before an invitation is issued.
Does the client have to log in every time?
No. The client accepts the invitation once. After that, the agent's periodically-refreshed credentials cover that client indefinitely, so there's no repeated client login for each submission.
Can authorisation be cancelled?
Yes. The agent can de-authorise a client, and the client can cancel the agent's authority or reject the initial invitation. Good software shows the invitation status — Invited, Accepted or Rejected — so you always know where you stand.
Related reading
Agent Services Account: Setup Guide for Accountants
What an Agent Services Account (ASA) is, why accountants need one for MTD, how to set it up, how it differs from the old agent accounts, and how it links to client authorisations.
MTD for Accountants: Getting Your Clients Ready
A practical readiness plan for accountancy practices — segmenting clients by threshold, fixing record-keeping habits, choosing software, managing authorisations, and pricing the extra quarterly work.
MTD for Income Tax Explained for Sole Traders (2026 Guide)
A plain-English guide to Making Tax Digital for Income Tax for sole traders — who's affected, what changes, what you have to do each quarter, and how to get ready before April 2026.