Connecting a client to HMRC for VAT with your agent account

Under Making Tax Digital a client’s VAT periods come from HMRC: once connected, Tax Optimiser pulls down their open and completed periods (HMRC calls them obligations) and you submit against them — you never type period dates in yourself. Every new client starts in demo mode, a safe sandbox where you can practise the whole journey without anything being sent to HMRC.

Practise in demo mode

Inside the client, open HMRC VAT → VAT Returns. A banner reminds you that nothing will be sent to HMRC. Click Connect to HMRC DEMO MODE.

The VAT Returns screen in demo mode with the Connect to HMRC DEMO MODE card

You’ll step through a simulation of HMRC’s real connection flow, so there are no surprises when you do it for real: press Continue, then Sign in on the dummy login (no credentials needed in demo mode), and finally Grant authority.

The dummy gateway explaining the steps before connecting to HMRC

The grant authority step of the dummy gateway

Back on VAT Returns you’ll see demo periods — one already Fulfilled (a completed return can’t be submitted against) and one Open awaiting data. In demo mode you can reset this sample data at any time with Actions → Reset Test Data.

The VAT Returns list showing an open period and a fulfilled period with their due dates and statuses

Switch to live mode

You do not need to sign the client up to Making Tax Digital for VAT before you file for real: HMRC signs up VAT-registered businesses automatically unless they are exempt, so there is no sign-up step and no confirmation email to wait for. When you’re ready, click the link in the demo banner and confirm Set to live mode.

Connect with your agent account

You then choose how to connect. The same choice is available any time from Actions → Reconnect to HMRC. As an accountant, pick Connect to HMRC using Agent Account — this uses your firm’s HMRC agent services account, so the one authority lets you view and submit VAT for this and every other client you act for. (The other option, Connect to HMRC (using Organisation Account), is for a business connecting its own Government Gateway login instead.)

The Connect to HMRC choice showing the Agent Account option alongside the Organisation Account option

You’re taken to HMRC’s gateway: press Continue, sign in with your agent Government Gateway credentials (HMRC may ask you to complete two-factor authentication), and finally Grant authority — this lets Tax Optimiser retrieve periods and submit returns on your behalf. The authority lasts 18 months; when it expires, reconnect from Actions → Reconnect to HMRC.

Your client’s VAT periods arrive

HMRC returns the client’s real VAT periods to the returns table. To work a period, click its link and follow the next article. We refresh periods intermittently, but if one you’re expecting hasn’t appeared — or you’ve just fixed an error — click Refresh from HMRC to re-pull everything.

Next: Upload, check and send a client’s VAT return.

Connect to HMRC: demo mode, then live with your agent account — in brief

VAT periods come from HMRC once connected - you never enter period dates yourself, and demo mode rehearses the whole flow safely.

There is no MTD for VAT sign-up step now: HMRC signs up VAT-registered businesses automatically unless they are exempt. Go live from the banner, then choose Connect to HMRC using the agent account to use your firm's agent services account.

One agent authority covers every client you act for and lasts 18 months; use Refresh from HMRC if an expected period has not appeared.