MTD ITSA quarterly deadlines and penalties: the firm’s guide

Making Tax Digital for Income Tax Self Assessment (MTD ITSA) went live for the £50,000+ cohort on 6 April 2026. For firms, the operational reality is no longer one filing season a year — it’s a rolling cycle of four quarterly windows per client, plus the Final Declaration, all governed by a points-based penalty regime imported wholesale from MTD VAT. This guide is for partners and ops managers running a landlord book at any meaningful scale.

The four quarterly windows

The statutory framework sits in the Income Tax (Digital Requirements) Regulations 2021, as amended by the 2024 and 2025 amending instruments. Regulation 8 sets the default quarterly periods aligned to the tax year, with submissions due one month and two days after the end of each period:

• Q1: 6 April – 5 July, submission due 7 August
• Q2: 6 July – 5 October, submission due 7 November
• Q3: 6 October – 5 January, submission due 7 February
• Q4: 6 January – 5 April, submission due 7 May

A client can elect for calendar-quarter periods (ending 30 June, 30 September, 31 December, 31 March) under the “calendar quarter election” in Regulation 9. The submission deadline shifts to the equivalent date — one month and seven days after period end — so 7 August through 7 May remain the four firm-wide dates that matter. The election must be made by the first submission of the tax year and cannot be revoked mid-year.

What a quarterly update is — and is not

A quarterly update is a cumulative summary of income and expenses per income source, by category, for the period to date. It is not a tax calculation. The figures can be revised in any subsequent quarter or in the Final Declaration without triggering a penalty for the original submission, provided the original was made on time. HMRC’s guidance is clear: the obligation is to submit, not to submit perfectly. This matters for how a firm chooses to run its review process — the bar for a quarterly is materially lower than the bar for the Final Declaration.

The Final Declaration

The Final Declaration replaces the SA100/SA105 for in-scope taxpayers. It is due by 31 January following the end of the tax year — so the 2026/27 Final Declaration is due 31 January 2028. It carries the full Self Assessment penalty framework: a separate late-filing penalty regime under Schedule 24 Finance Act 2021, and the established late payment penalties under Schedule 26 FA 2021. Payment dates are unchanged — balancing payment on 31 January, payments on account on 31 January and 31 July.

The Final Declaration is where the substantive tax adjustments land: the Section 24 finance cost restriction, capital allowances, the property income allowance, loss utilisation, and any out-of-scope income (employment, savings, dividends, capital gains). Firms should treat it as the historical annual return — the quarterly updates are a feeder process, not a substitute for the year-end work.

The points-based penalty regime

The flat-rate late-filing penalties that applied to legacy Self Assessment do not apply to quarterly updates. Instead, quarterly updates fall under the points-based regime in Schedule 24 Finance Act 2021, with HMRC guidance at CH192000 onwards in the Compliance Handbook. The mechanics are the same as those that have been operating for MTD VAT since January 2023.

How points accrue

Each missed quarterly update earns the taxpayer one point. Points accrue separately for each “submission obligation” — in MTD ITSA that means one points total for the quarterly updates and a separate points total for the Final Declaration. For an in-scope landlord with one property income source, the quarterly threshold is four points in a rolling assessment period. Once the threshold is reached, a £200 fixed penalty is charged, and a further £200 for each subsequent missed submission until points are reset.

How points are reset

Points are removed in two ways. First, a single point expires automatically after 24 months if the threshold has not been reached. Second, once at the threshold, the whole points total is wiped only after the taxpayer has both (a) submitted every required return on time during a defined “period of compliance” — 24 months for annual obligations, 12 months for quarterly — and (b) brought all outstanding submissions for the previous 24 months up to date. In practice, a client at threshold needs a full clean year to get back to zero. CH192100sets out the mechanics.

Reasonable excuse and appeals

The reasonable excuse provisions in paragraph 20 of Schedule 24 FA 2021 apply. Firms should keep a clean evidence trail when relying on reasonable excuse: the bar HMRC applies in practice — particularly post-VAT — is closer to the long-standing CH61500 line than to anything generous. Software failure on the client’s side is rarely accepted. Bereavement, serious illness and HMRC system outages generally are. Points can be appealed within 30 days of the notification.

Worked example: a firm with 80 landlord clients

Take a regional firm with 80 landlord clients in the £50k+ cohort — all in scope from 6 April 2026, all subject to four quarterly submissions per year. That’s 320 submission events per tax year on the quarterly cycle alone, before the Final Declarations.

Suppose Q1 goes badly: 12 clients are one day late for the 7 August deadline — chasing dragged, a couple of bank-feed reconnections failed, two clients went on holiday. Each of the twelve clients picks up one penalty point. None of them is at the four-point threshold yet, so no monetary penalty is charged.

The cost to the clients in Q1 is zero. The cost to the firm is the 12 newly accrued points sitting on client records — each one burning down only after 24 months, and only on the condition that the other three quarters of the year land cleanly. If those twelve clients are also one day late at Q2, that’s a second point each. By Q3, on the same pattern, the firm is one missed quarter away from twelve £200 penalties, plus a further £200 per missed submission for the rest of the year, plus the reputational consequence of having put twelve clients into a 12-month period-of-compliance to get back to zero.

The arithmetic the partner cares about: the marginal cost of letting a quarterly slip is not the penalty itself — it’s the loss of headroom for the rest of the year. A book of 80 clients realistically needs a one-week buffer baked into every quarterly window and a deterministic chase cadence that starts at period-end, not at deadline-minus-three-days.

Operational implications for the firm

Submission obligations are per-source, not per-client

A client with both self-employment and UK property income has two submission obligations — one for each source — but they fall under the same quarterly points total. A client with two property businesses (for example UK property and a furnished holiday let business — to the extent any FHL-style treatment continues to apply post-abolition) and a sole-trader business sits at three quarterly submissions per period. The firm’s job sizing should be done on submission count, not headcount.

The chase window is the binding constraint

The hard date is the 7th of the second month after period end. In practice the firm needs records in hand by the 25th of the first month after period end to leave a working week for review. For landlord clients, the binding constraint is almost never the submission step — it’s getting bank transactions, mortgage interest figures and any missing receipts out of the client. A firm running 80+ landlord clients on the £50k+ cohort needs the chase to start the day the quarter closes.

Final Declaration is the substantive review point

Quarterly figures are revisable. The Final Declaration is where the firm signs off on what counts as an allowable expense, how Section 24 has been applied, capital allowances on any qualifying assets, and the interaction with non-MTD income. Treating the Final Declaration as “just another quarter” is the most common operational failure pattern firms have hit in the MTD VAT regime; the substance hasn’t gone away — it’s moved out of the quarterly process and into the annual sign-off.

What firms should put in place now

1. A submission obligation register, not a client register. One row per source per client, with the quarterly cadence, the calendar/tax-year election, and the current points balance. Driving the workflow from a client list rather than an obligation list is what causes Q1 slippage.
2. A deterministic chase cadence. First contact at period end, second at +10 days, escalation at +20. The consequence of letting clients dictate timing is twelve avoidable points across the book.
3. A bank-feed health check on the 1st of every quarter. A broken feed is the single most common reason for late quarterly submissions in the early MTD VAT data, and the failure mode is silent.
4. A Final Declaration calendar that runs from the following 6 April, not from December. The Final Declaration workload is the old annual return workload — quarterlies do not displace it, they precede it.
5. A points dashboard visible at partner level. Points balances are public information once HMRC’s agent services account exposes them; firms that monitor them quarterly catch the slow drift to the threshold before it crystallises into £200 penalties.

See also our companion guide on what changes from 6 April 2026 for the underlying scope and digital record-keeping requirements.