How to Add a Client and Send an HMRC Authorisation Request
For accountants: how to add a client in ThisQuarter, pass HMRC's proof-of-knowledge check, and send an authorisation request so you can file for them under your Agent Services Account.
The short answer
To act for a client, add them in ThisQuarter (Clients → Add client) with their name as HMRC holds it, National Insurance number, date of birth and postcode — HMRC's proof-of-knowledge check. Then send an authorisation request: HMRC invites the client, who accepts once via their own Government Gateway login. After acceptance, your Agent Services Account connection covers that client indefinitely — no repeated client logins.
Before you can file for a client, HMRC needs the client to grant you authority. This guide walks accountants through adding a client in ThisQuarter and sending the one-time authorisation request.
First: connect your Agent Services Account
Make sure ThisQuarter is connected to HMRC via your Agent Services Account (Settings → HMRC Connection). This single connection covers all your clients — you don't reconnect per client. See the guide on connecting to HMRC if you haven't done this yet.
Step by step
- Add the client — Clients → Add client. Enter their name as HMRC holds it, National Insurance number, date of birth, postcode and (recommended) UTR.
- Send the authorisation request — HMRC generates an invitation; use Copy link to send it to the client.
- Client accepts once via their own Government Gateway login.
- Status moves to Accepted — you can now act for them.
- Select the client in the client switcher and start filing.
HMRC's proof-of-knowledge check
The details you enter aren't just a record — HMRC uses them to confirm you know
the client (their name, NINO, date of birth and postcode). Enter the name
exactly as HMRC holds it (e.g. Mr J Smith) so the check passes.
What acceptance unlocks
- The first client you get authorised also triggers a one-time, broader agent-authority grant from HMRC. Later clients don't repeat that step.
- You can act as a main or supporting agent — ThisQuarter links to HMRC's guidance on the difference.
- You can de-authorise a client at any time, and the client can cancel their invitation from their side.
Troubleshooting
- The check fails: confirm the name matches HMRC's records exactly and the NINO, date of birth and postcode are correct.
- The client can't find the invitation: resend the link, and make sure they're signing in with their own Government Gateway (not yours).
Once the client is authorised, see the guides on submitting a quarterly update and, at year-end, completing the final declaration.
Step by step
- 1
Connect your Agent Services Account first
Make sure ThisQuarter is connected to HMRC via your Agent Services Account (Settings → HMRC Connection). This one connection covers all your clients.
- 2
Add the client
Go to Clients → Add client. Enter the client's name exactly as HMRC holds it, their National Insurance number, date of birth, postcode and (recommended) their UTR. These double as HMRC's proof-of-knowledge check.
- 3
Send the authorisation request
Start the authorisation request for the client. HMRC generates an invitation — use Copy link to send it to the client, or HMRC notifies them directly.
- 4
Client accepts once
The client opens the invitation and accepts it once using their own Government Gateway login. You'll see the status move from Invited to Accepted.
- 5
Start filing
Once accepted, your agent authorisation covers that client. Select them in the client switcher and begin retrieving obligations, entering figures and submitting updates.
Frequently asked questions
What details do I need to add a client?
The client's name exactly as HMRC holds it, their National Insurance number, date of birth and postcode — these form HMRC's proof-of-knowledge check. Their UTR is optional but recommended. ThisQuarter validates the NINO and UTR formats as you type.
Does the client have to log in every time I file?
No. The client accepts your authorisation request just once via their own Government Gateway. After that, your Agent Services Account connection (which refreshes automatically) covers them indefinitely — no repeated client logins.
What are the invitation statuses?
Invited (sent, awaiting the client), Accepted (the client granted authority — you can now file), and Rejected (declined). ThisQuarter shows the current status per client so you always know where you stand.
Can I stop acting for a client?
Yes. ThisQuarter provides an 'Agent de-authorises client' action, and a client can cancel their invitation from their side. Either removes your authority to act for them.
Why is the client's NINO locked after I've filed?
Once a submission has been made to HMRC under a client's National Insurance number, that NINO is tied to the filings and can't be changed. You can still update the client's name, date of birth, address and UTR.
Related reading
How to Complete Your Final Declaration in ThisQuarter
The year-end step by step: add your non-business income and reliefs, trigger and review HMRC's tax calculation, and submit the final declaration that replaces the SA100 — all in ThisQuarter.
How to Review and Amend a Submitted Quarterly Update
How to correct a quarterly update you've already filed in ThisQuarter — unlocking the period, amending the cumulative figures, resubmitting to HMRC, or cancelling to restore the filed version.
How to Import Your Figures from a Spreadsheet into ThisQuarter
Bring your income and expenses into ThisQuarter from Excel or CSV — how the labelled import works, how to check the preview before applying it, and how it feeds straight into your quarterly update.