The first time you try to submit a VAT return or an MTD ITSA update, you'll be asked to connect your HMRC account. It's a standard OAuth flow, takes about a minute, and only happens once.
What happens when you click connect
- We redirect you to www.tax.service.gov.uk — HMRC's own login screen.
- Sign in with your Government Gateway user ID and password.
- HMRC asks you to authorise AccountantUK to read your VAT / ITSA obligations and submit returns on your behalf.
- You're returned to AccountantUK with the OAuth token saved against your account.
What the token does
We store an encrypted refresh token that lets us call HMRC's MTD APIs without asking for your password again. The token rotates every 18 months — we re-prompt you automatically before it expires.
Disconnecting
Settings → Integrations → HMRC → Disconnect. We delete the token; we can't talk to HMRC for you again until you reconnect.
Common gotchas
- Wrong Gateway account — make sure you sign in with the Gateway ID for the business you manage in AccountantUK, not your personal one.
- Agent credentials are different — accountants filing for clients need agent services account credentials. The agent flow has a separate prompt.
- Not enrolled in MTD yet — for VAT you must already be enrolled; for ITSA, we enrol you when we submit your first quarterly update.