MTD for Income Tax: what changes for accountants and their clients

Who is in scope, and when

Making Tax Digital for Income Tax Self Assessment (MTD ITSA) is being phased in by income level, based on a taxpayer's qualifying income — gross income from self-employment and property, before expenses — reported in an earlier tax year:

Below £20,000, taxpayers stay on the traditional annual Self Assessment return for now, though the direction of travel is clearly toward eventually including them. Qualifying income is assessed from the tax return roughly two years before the mandation date — so a sole trader or landlord's 2024/25 return determines whether they're mandated from April 2026, and HMRC writes to affected taxpayers based on that assessment. Crucially, qualifying income is gross, not profit — a landlord with high rental turnover and thin margins can be well inside scope despite modest actual profit.

General partnerships were originally in the same phased scope but have been deferred with no date yet confirmed — worth flagging to any partnership clients who assumed they were included on the same timetable as sole traders and individual landlords.

What actually changes

MTD ITSA doesn't just move the same annual return online — it replaces the single annual submission with a new rhythm:

• Digital records — income and expenses must be kept digitally, in MTD-compatible software (a spreadsheet can qualify only if paired with bridging software that submits directly).
• Quarterly updates — a running summary of income and expenses submitted to HMRC roughly every three months, for each qualifying trade or property business.
• End-of-period statement (EOPS) — a year-end finalisation per business, confirming and adjusting the quarterly totals.
• Final declaration — replaces the old SA100 as the taxpayer's overall declaration, pulling together all businesses plus any other income (employment, dividends, pensions) not otherwise in MTD.

The quarterly updates are a running total, not a tax calculation in themselves — no tax is due quarterly under the standard MTD ITSA rules (this is a common client misconception worth correcting early); the actual liability is still settled through the normal Self Assessment payment dates, based on the final declaration.

The quarterly cycle

Standard quarters run to fixed calendar dates regardless of a business's accounting year end, with each update due one month after the quarter closes:

A taxpayer with more than one qualifying business (say, a sole trader who also lets a property) submits a separate quarterly update per business, on the same four dates — which multiplies the practice's submission workload per client rather than the client count.

The penalty regime — points-based, not strike-first

Late submission under MTD ITSA uses a points-based system rather than an automatic fine for every miss: each late submission (quarterly update, EOPS or final declaration) earns a point, and only on reaching a threshold (4 points for quarterly filers) does a fixed £200 penalty apply — after which every further late submission triggers another £200 penalty directly, without needing to rebuild points. Points expire after a period of on-time compliance. Late payment penalties are separate and layered by how late the payment is, with interest running throughout. A soft-landing period reduces the practical bite of the new regime in the first year(s) after mandation for a given income band — but "soft landing" affects penalty application, not the underlying submission deadlines themselves, which apply from day one of mandation.

What practices are actually doing to prepare

The practices handling MTD ITSA smoothly are treating it as a workflow and client-communication problem more than a technical one:

• Segmenting clients by mandation date now, rather than waiting until each cohort is imminent — a client just under the £50,000 threshold today may cross it before 2027 or 2028 and needs monitoring, not a one-off check.
• Moving bookkeeping onto MTD-compatible software well before the mandation date, so the first live quarter isn't also the client's first time using digital record-keeping.
• Building the quarterly cycle into the practice's own calendar as four hard client-facing deadlines a year, not folding it into the existing annual peak — the workload doesn't move to April, it spreads (unevenly) across the whole year.
• Setting client expectations early that quarterly updates are not a tax bill — this single point of confusion generates more client queries than almost anything else about the new regime.

Because MTD ITSA adds four fixed deadlines a year per business rather than one, the practical failure mode isn't usually understanding the rules — it's a deadline slipping past unnoticed across dozens of clients, each with a different mandation start date and possibly more than one qualifying business. A structured deadline register, fixed against each client's actual obligations rather than tracked from memory, is what actually prevents that. FinanceIQ keeps this alongside a practice's other statutory deadlines (VAT, CIS, PAYE, Self Assessment) in one register, with the quarterly MTD ITSA dates and the current soft-landing penalty position applied automatically.

Common mistakes

1. Assuming qualifying income means profit — it's gross income, which catches more landlords and traders than expected.
2. Telling clients a quarterly update means quarterly tax payment — it doesn't, under the standard rules.
3. Not monitoring clients just below a threshold, who may be mandated sooner than assumed.
4. Leaving software migration until the mandation date itself, rather than running it in parallel beforehand.
5. Missing that multi-business clients (trade + property) file a quarterly update per business, not one combined update.

This guide is general information, not legal, tax or compliance advice. Rules change — always check the current official guidance for your situation.