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Getting StartedMaking Tax DigitalUpdated February 19, 2026

Blog: Connecting to HMRC — OAuth 2.0 Authentication Now Live

Connecting to HMRC — OAuth 2.0 Authentication Now Live (v1.0.4)

With the release of v1.0.4, the platform now supports a full OAuth 2.0 integration with HMRC's Making Tax Digital (MTD) API. This is the foundational step that makes everything else possible — quarterly submissions, income reporting, and full MTD compliance for UK landlords.

Why This Matters

HMRC's Making Tax Digital programme requires landlords with income above the threshold to submit quarterly updates digitally, using HMRC-approved software. That software must connect to HMRC's API using their mandated OAuth 2.0 flow — there is no alternative path.

Until this release, the platform could import and organise your property transaction data (via your AgentOS landlord record), but had no way to actually send that data to HMRC. v1.0.4 closes that gap. Every MTD submission feature that ships from here forward is built on this authentication layer.

What's Been Built

One-Time Authorisation

Landlords go through the HMRC OAuth flow once. You'll be redirected to HMRC's Government Gateway, where you log in and grant the platform permission to submit on your behalf. After that, you're connected — no repeated logins, no manual token handling.

National Insurance Number — A Required Step

HMRC uses your National Insurance Number (NINO) to identify you as a taxpayer in the MTD system. As part of the authorisation handshake, you'll be asked to provide your NINO. This is stored securely against your landlord record and included automatically in all HMRC API calls that require it.

This is not optional — HMRC will reject any MTD submission that cannot be matched to a valid NINO.

Tokens That Manage Themselves

OAuth access tokens expire. Historically, this has been a source of friction in API integrations — submissions fail silently, users get confused. We've handled this properly from day one:

  • Access tokens are stored per landlord in isolation.
  • The platform automatically refreshes tokens before they expire using the refresh token.
  • You will not be interrupted mid-quarter by an expired credential.

What You Need to Get Started

  1. An HMRC Government Gateway account enrolled for MTD for Income Tax.
  2. Your National Insurance Number — you'll be prompted for this during authorisation.
  3. Nothing else. The platform handles the rest.

Head to your account settings and look for "Connect to HMRC" to begin the authorisation flow.

What's Next

With authentication in place, the next releases will build directly on top of this foundation:

  • Quarterly update submissions — sending your income and expense figures to HMRC each quarter.
  • End-of-period statements — finalising each tax year with HMRC.
  • Transaction import from AgentOS — pulling your landlord record data directly into the submission pipeline.

v1.0.4 is the infrastructure. Everything visible to landlords is coming next.

For technical detail on how the OAuth flow works and how tokens are managed, see the HMRC MTD API Authentication documentation.