From 6 April 2026 onwards, the way you authorise an accountant to file your MTD ITSA quarterly updates is the Agent Services Account, not the older 64-8 form. The change is not optional, the new route is digital end to end, and the gov.uk landlord-facing guidance on the authorisation handshake stops short of three landlord-side failure modes that catch most first-time users. This page walks the authorisation step by step from your inbox to confirmation that the agent is active in your Government Gateway account, then covers the joint-owner case, the accountant-change case, and the in-flight cessation case where your accountant firm dissolves mid-quarter.

Why the 64-8 form won't work for MTD ITSA

The 64-8 paper authorisation route remains valid for non-MTD tax services. Annual self-assessment for landlords below the MTD threshold, corporation tax, VAT in older formats, PAYE, all continue under 64-8 unchanged. For MTD ITSA specifically, HMRC requires the Agent Services Account (ASA), which is a digital authorisation tied to the MTD ITSA service. A 64-8 in force for your self-assessment does not extend to MTD ITSA; the two authorisations are separate, granted on separate flows, recorded against different agent identifiers at HMRC's end.

The practical implication: if your accountant has represented you for years under a 64-8 for self-assessment, that authorisation does not migrate. They need to obtain fresh ASA authorisation for MTD ITSA before they can file your quarterly updates from 6 April 2026 (or your first mandate date, depending on your threshold cohort). The two authorisations then run in parallel; the 64-8 continues to cover whatever it was filed for, the ASA covers MTD ITSA.

What the Agent Services Account actually is

An Agent Services Account is HMRC's digital container for agent-firm authorisations on the newer service portfolio (MTD services, the trust registration service, the income record viewer for agents, and others added over time). One ASA per agent firm; client authorisations flow into the ASA and remain there as long as the client has authorised the firm and the firm meets the ongoing registration requirements (UK-based tax adviser, anti-money-laundering supervision, current registration with HMRC).

From your side as a landlord, you do not interact with the ASA directly. You authorise the firm via a digital handshake initiated by them, and once authorised, the firm holds your authorisation in their ASA for as long as you do not revoke it. The authorisation gives them the technical ability to call HMRC's MTD ITSA APIs on your behalf (quarterly updates, end-of-period statement, final declaration), to view your MTD ITSA data, and to act for you in MTD ITSA correspondence.

The handshake at a glance: five steps

  1. Your accountant signs into their ASA and requests authorisation for you, entering your name, UTR, and email address.
  2. HMRC sends you an email with a unique authorisation link.
  3. You click the link, sign in via your Government Gateway credentials, and see an approval screen.
  4. You click Approve. HMRC records the authorisation and notifies the accountant.
  5. The accountant verifies the authorisation appears as active in their ASA; you verify it appears in your Government Gateway 'Manage my agents' view.

Median time end to end where the landlord acts promptly: under an hour. Plan 1 to 2 weeks ahead of any filing deadline, not the day before; verification delays at any of steps 2, 3, or 5 can push the timeline into multiple days.

Step 1: your accountant sets up the ASA (their side, briefly)

This step is the accountant's responsibility, mentioned here only so you know what they are doing. To set up an ASA, the accountant firm needs Government Gateway credentials for the firm, the firm's UTR and registered-office postcode, the company registration number (if a limited company), VAT registration number (if VAT-registered), evidence of anti-money-laundering supervisory body registration, and the firm's principal-contact details. HMRC then reviews and creates the ASA, normally within a few days for a complete application.

From your perspective, you do not need to verify or audit the accountant's ASA setup. The fact that they are operating as a UK tax-adviser firm with HMRC-registered status is the practical comfort. If you are evaluating a new accountant, confirming they hold an active ASA for MTD ITSA is reasonable due-diligence (ask the question directly; established firms answer in a sentence).

Step 2: the authorisation request lands in your email

Once your accountant has initiated the request, HMRC's automated system sends an email to the address your accountant entered. The email is from a `noreply.gateway.gov.uk`-style address and contains a unique authorisation link. The email is the single most common failure point in the whole flow; misclassification as spam, mistyped email address at the accountant's end, or HMRC verification flagging are the three usual causes.

  • Spam / junk filter. Check spam and junk folders before reporting the email as missing. Automated HMRC emails from no-reply addresses commonly misclassify as spam, especially on stricter corporate inboxes.
  • Wrong email address. If the accountant entered the wrong address in the request, the email will not arrive. Contact the accountant; they can re-issue with the corrected address (the original request is left to expire on its 14-day timeout).
  • HMRC verification flag. Government Gateway occasionally requires identity verification before authorisation requests are released to you. The flag clears after you complete the verification step, then HMRC re-issues the email.

Step 3: signing in via Government Gateway and approving

Clicking the link in the email takes you to a gov.uk authorisation page. You sign in with your existing Government Gateway credentials (the same login you use for self-assessment, MTD VAT if you have it, the personal-tax account, etc). After sign-in, you see a confirmation screen showing the agent firm name, the tax service the agent is requesting access to (`Making Tax Digital for Income Tax`), and two buttons: Approve or Reject.

Approve completes the authorisation. The screen confirms the approval, HMRC records it against your account, and the system notifies your accountant. Reject sends a rejection back to the accountant; useful if you do not recognise the firm or did not expect the request. There is no partial-approval option for the MTD ITSA service; the authorisation is full-service or none.

If you have multiple Government Gateway credentials (a common situation for landlords who have set up separate accounts at different times), make sure you sign in with the credentials linked to your MTD ITSA enrolment. Signing in with the wrong credentials returns an error and stalls the flow; if uncertain, the credentials you use for self-assessment are usually the right ones, as MTD ITSA enrolment is typically attached to your existing SA UTR.

Joint owners and spouses: each authorises separately

A jointly owned rental property where both spouses are in MTD ITSA generates two MTD filings, and each spouse must authorise the accountant separately. There is no "spouse-implies-spouse" rule; one spouse's authorisation does not extend to the other. Operationally, this means your accountant generates two ASA requests when onboarding a couple, you each receive a separate email, you each sign in with your own Government Gateway credentials, you each approve.

Two practical points for couples. First, schedule the two approvals at the same time where possible (one shared screen, both Government Gateway logins ready). Splitting the approvals across days is operationally fine but introduces a window where one filing is authorised and the other is not, which can confuse the first quarterly cycle. Second, if one spouse has lost track of their Government Gateway credentials, recover them before the authorisation email goes out, not after; password reset on Government Gateway can take several days for identity verification, which delays the authorisation flow.

The wider operational mechanics of joint-owner MTD filings (the two-cycle architecture, bookkeeping discipline, mid-year split changes) are covered in our dedicated joint-owner quarterly-filing mechanics page; this page covers the authorisation step specifically.

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Three failure modes gov.uk glosses over

The gov.uk guidance describes the happy-path flow cleanly. Three failure modes that catch landlords are not covered by the public guidance and are worth knowing about in advance.

Failure mode 1: the email-address mismatch with the MTD ITSA enrolment. If your MTD ITSA enrolment at HMRC's end is registered against an old email address (one you have not used for years), the authorisation email may go to that old address even though your accountant entered your current address. The fix is to update your email at the Government Gateway side before the authorisation request goes out, which involves signing into your personal-tax account and updating contact details. Do this 1 to 2 weeks ahead of the authorisation if you suspect your registered email may be out of date.

Failure mode 2: the partially-completed Government Gateway profile. Some landlords have Government Gateway credentials but have never enrolled for MTD ITSA. When they click the authorisation link, the gov.uk flow asks them to enrol for MTD ITSA before the approval screen renders, which can stall the authorisation by hours or days depending on identity-verification requirements. If you have never enrolled for MTD ITSA, enrol first (via the standard self-service flow), then deal with the authorisation. Our how-to-register MTD landlord page covers the self-enrolment step.

Failure mode 3: the in-flight expiry. Authorisation requests expire after 14 days. If you delay clicking the email beyond the expiry window, the request lapses and your accountant has to re-issue. The clock starts at the moment your accountant submits the request, not the moment you receive the email; bad email delivery delays effectively shrink the window. Treat the request as time-sensitive; if you cannot action it within 7 days, ask your accountant to re-issue rather than risk the expiry.

Changing accountants: revoke + re-authorise (not transfer)

ASA authorisations do not transfer between accountants. If you switch firms, two steps:

  1. Revoke the old firm's authorisation. Sign into your Government Gateway, navigate to 'Manage my agents', find the old firm under the MTD ITSA line, and remove the authorisation. The revocation takes effect immediately; the old firm loses the ability to file or view your data from that moment.
  2. Authorise the new firm. The new firm initiates an ASA authorisation request (same flow as initial onboarding); you receive an email, sign in, approve. The new firm then has authority going forward.

Mid-cycle accountant changes have to be co-ordinated to avoid a gap in quarterly filings. If you are switching at a calm period (between quarters, well before the next deadline), the gap is procedural and no submissions are at risk. If you are switching with a quarterly deadline imminent, the old firm typically completes the in-progress quarter under their authorisation, the new firm picks up from the next quarter. Get explicit clarity on who is filing which quarter; treating this implicitly is the most common cause of missed-deadline penalties at accountant changeover.

The in-flight cessation case: agent firm dissolves mid-quarter

An infrequent but high-impact scenario: your accountant firm dissolves, is struck off, or otherwise closes its ASA mid-quarter. HMRC processes the firm's notification of cessation, which closes the firm's ASA and terminates all authorisations the firm held. Your authorisation lapses; pending submissions held in the firm's account do not migrate.

Three steps to recover:

  1. Export your data from the firm before the closure date. If you have advance notice that the firm is winding down, get the year-to-date digital records exported in a format that can be imported into your own MTD-compatible software or a successor accountant's product. CSV export of the source ledger is the safest format; vendor-specific backups are often unreadable outside the original product.
  2. Authorise a replacement accountant under a new ASA flow. This is the standard ASA onboarding (steps 1 to 3 above); the replacement firm picks up your representation under their authorisation.
  3. Catch up on any missed quarterly updates. If the cessation gap caused you to miss a quarterly deadline, file as soon as the new authorisation is live and consider whether to appeal the points penalty on reasonable-excuse grounds (the firm dissolution is generally an accepted reasonable excuse, but you must demonstrate prompt action on the replacement).

The MTD obligation remains on you as the taxpayer regardless of the firm's status; HMRC does not give grace periods for agent-firm failures beyond the reasonable-excuse appeal route. Plan for continuity; for accountants on shaky operational footing, an early conversation about backup arrangements is worth having.

Verifying the authorisation actually landed

The clean verification step is in your Government Gateway. Sign in, navigate to 'Manage my agents' under Account settings, and look for the agent firm name alongside the `Making Tax Digital for Income Tax` service label. If the firm appears with that label, the authorisation is active and your accountant can file on your behalf.

If the firm expects to be authorised but does not appear, the most likely cause is that the request failed somewhere in the email-approval flow (steps 2 or 3 above). Re-issue from the accountant side and re-run the approval. Do not rely on the accountant's confirmation as the definitive sign-off; the Government Gateway 'Manage my agents' view is the canonical record. We recommend confirming via Government Gateway specifically in the first quarter after onboarding, as authorisation drops or partial completions are most likely to surface there.

Where this page sits

The ASA authorisation is one operational sub-step in the MTD ITSA onboarding journey. If you are still calibrating whether MTD ITSA applies to you, the six headline changes for residential landlords covers the regime shape, and the HMRC letter action page covers the verify-and-act flow if HMRC has written to you specifically. The how-to-register MTD landlord page covers the landlord self-enrolment flow, which is separate from the agent authorisation flow this page covers.

For the practical follow-through (which software to use, how the quarterly cycle runs once the authorisation is in place), see our MTD software decision-tree page and the quarterly deadlines page for the calendar of filing dates. Joint-owner couples should pair this authorisation walkthrough with the joint-owner quarterly-filing mechanics page for the two-parallel-cycle operational picture.

The bottom line on ASA authorisation

The Agent Services Account is the mandatory route for MTD ITSA agent representation from 6 April 2026; the older 64-8 does not extend to MTD. The handshake is five steps: accountant requests, HMRC emails you, you sign in, you approve, both sides verify. Joint owners each authorise separately. Authorisations do not transfer between firms; switching accountants requires revoke and fresh authorisation. The 'Manage my agents' view in your Government Gateway is the canonical verification mechanism; check it in the first quarter after onboarding and at any point of doubt thereafter.