MTD for Income Tax carries no requirement to use an accountant
Making Tax Digital for Income Tax has applied to sole traders and landlords with qualifying income over £50,000 since 6 April 2026, and nothing in that regime obliges anyone to appoint an accountant. HMRC recognises free software for people with simple tax affairs, publishes step-by-step guidance on sending quarterly updates, and accepts submissions made directly by the taxpayer. A CIS subcontractor who wants to file everything themselves is entitled to do so.
The useful question is therefore not whether you are allowed to self-serve, but whether you should. This guide separates the two things people merge into one when they ask it: MTD compliance, which is largely a software problem, and CIS tax accuracy, which is where money is actually won or lost. It sets out the annual workload, who can genuinely handle it alone, where a specialist earns its fee, and the break-even arithmetic on real 2026/27 figures.
What MTD actually asks a CIS subcontractor to do each year
The obligation has three parts, and none of them is individually difficult. The volume and the reconciliation are what make it a job rather than a task.
- Digital records. Income and expenses recorded in MTD-compatible software as they arise, not typed up from a shoebox after the year end. Bridging software lets you keep spreadsheets and submit from them, so existing systems are not automatically wasted.
- Four quarterly updates. Cumulative totals of income and expenses per business, submitted to HMRC. These are summaries, not returns: HMRC does not receive individual invoices or receipts.
- A year-end tax return submitted through the same software by 31 January following the tax year, confirming the final figures and picking up anything outside the quarterly cycle.
The quarterly deadlines for standard update periods aligned to the tax year are fixed and easy to plan around.
| Update period (standard) | Submission deadline | Typical construction context |
|---|---|---|
| 6 April to 5 July | 7 August | Peak season, highest invoice volume |
| 6 July to 5 October | 7 November | Summer works completing, materials spend high |
| 6 October to 5 January | 7 February | Falls a week after the 31 January payment date |
| 6 January to 5 April | 7 May | Year-end tidy-up, capital purchases often land here |
Calendar quarters ending 31 March are also permitted and carry the same four deadlines. Whichever you pick, the cycle repeats every year, which is the real change: annual admin has become quarterly admin.
Who can genuinely self-serve on MTD as a subcontractor
Self-filing is a sensible choice, not a failure of ambition, where all of the following hold true.
- One trade, one income stream, no second business and no property income to report separately.
- No employees, no subcontractors of your own, so no CIS300 monthly returns and no payroll.
- Sole trader, not a limited company, so no corporation tax return, no payroll and no Employer Payment Summary reclaim to manage.
- Not VAT registered, so no domestic reverse charge decisions on every invoice.
- A short, evidenced expense list you already understand, and CIS payment and deduction statements arriving reliably from every contractor who pays you.
- Comfort with software: bank feed connected, receipts photographed on site, reconciliation done monthly rather than annually.
Break any two of those and the calculation changes quickly. A subcontractor who becomes a contractor mid-year, registers for VAT, or incorporates has added obligations that MTD software will not think about on their behalf.
Where the software stops and a CIS specialist starts
MTD-compatible software is genuinely good at what it does. It holds digital records, categorises transactions, calculates quarterly totals and submits them. What it does not do is exercise judgement, and CIS is a judgement-heavy scheme.
Software will submit whatever you enter. It will not flag that a contractor has applied the 20% deduction to your whole invoice rather than the labour element only, which is the most expensive routine error in the scheme and one that costs a subcontractor real money on every affected payment. It will not notice that your CIS deduction statements total £11,400 while the deductions recorded against your income entries total £10,900, a gap that surfaces at the year end as an underclaimed refund. It will not tell you that the £4,200 van you bought in March qualifies for a full capital allowance claim in year one rather than a slow write-down.
Nor does compliance software have a view on structure. The most valuable conversations a construction business has in a year are about whether the numbers now support gross payment status, whether incorporation makes sense, and whether the EPS route would recover deductions in-month instead of a year later. Those are advisory questions, and quarterly filing has not created them, it has only made the underlying record accurate enough to answer them properly.
Our guide to what a CIS accountant does covers the wider service question and market fee benchmarks. The narrower MTD question is the one below.
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The cost side: software, hours and the MTD penalty exposure
Three costs sit on the self-serve side of the ledger, and only one of them shows up on a bank statement.
Software. Free products exist for simple affairs, generally with limits on transaction volume or features. Paid construction-friendly packages are commonly quoted around £10 to £30 a month across the market (a trade-reported range, not a fixed price), sometimes with a CIS module charged separately. Our comparison of the best CIS accounting software ranks the main products against CIS-specific criteria, and if you are still on spreadsheets, spreadsheets versus accounting software for CIS workers covers the bridging option.
Your hours. This is the cost most subcontractors leave out of the sum. Reconciling a quarter of contractor statements, categorising expenses and reviewing the figures before submission is not a five-minute job in a trade with multiple contractors, split labour and materials invoicing, and materials receipts from three merchants. Whatever that time is worth to you, it is an hour not spent on site.
Penalty exposure. The 2026/27 easement is narrower than it sounds, and it expires.
| Event | 2026/27 | 2027/28 onwards |
|---|---|---|
| Late quarterly update | No penalty points | 1 point per missed deadline; £200 at 4 points, then £200 per further miss |
| Late tax return | Penalty point applies | Penalty point applies |
| Tax unpaid at day 15 | 3% of the amount outstanding | 4% of the amount outstanding |
| Tax still unpaid at day 30 | A further 3% | A further 4% |
| Tax unpaid from day 31 | 10% a year, charged daily, up to 2 years | 10% a year, charged daily, up to 2 years |
The first year of the late payment regime gives 30 days from the due date to pay or contact HMRC before penalties start, reducing to 15 days thereafter. Read the grace correctly: it removes penalty points for late quarterly updates in year one only. It does not touch late payment penalties, interest, or the return deadline.
The break-even sum for a CIS subcontractor
The honest framing is not fee against zero. Nobody chooses between an accountant and nothing. The choice is between an accountant and the combination of software cost, your own hours, and the difference in outcome. The illustration below uses a sole trader subcontractor on £58,000 gross labour income in 2026/27, with figures rounded for clarity.
| Line | Self-serve | Specialist engaged |
|---|---|---|
| MTD software | £240 a year (£20 a month) | Often bundled in the fee |
| Your time on the quarterly cycle | Roughly 4 hours per quarter plus 6 hours at the year end, so about 22 hours | Roughly 1 hour per quarter reviewing, so about 5 hours |
| Value of the 17 hours saved, at an illustrative £30 an hour of chargeable time | Nil | About £510 |
| Expense categories captured | What you know to claim | Full review including capital allowances, mileage at 55p, subsistence tests |
| Reconciliation of CIS deduction statements | Yours to do | Checked line by line against contractor statements |
| Penalty and interest risk | Carried by you | Deadline management included |
On those illustrative figures the fee has to be beaten by only two things to justify itself: the hours released back into chargeable work, and the difference in the final tax position. On a typical CIS refund of £2,000 to £3,000 (an illustrative market range, not a guarantee), a few hundred pounds of expense categories that a self-filed return misses will often close the gap on its own. Where the numbers do not work is the genuinely simple case: one contractor, few expenses, a subcontractor who is comfortable in the software and files on time. That subcontractor should self-serve, and should revisit the decision the year anything changes.
Before deciding either way, put your own numbers through the CIS refund estimator. Knowing the size of the refund at stake is what turns this from an opinion into arithmetic.
Five triggers that move the answer for a CIS subcontractor
Rather than a general rule, watch for the specific events that change the calculation.
- You start paying subcontractors. You become a contractor, with CIS300 monthly returns by the 19th, verification obligations, and nil returns for every month with no payments from 6 April 2026. MTD software does not carry that obligation for you.
- You incorporate. A limited company falls outside MTD for Income Tax on its trading profits, but gains corporation tax, payroll, annual accounts and the EPS route for recovering CIS deductions in-month. The compliance load rises even as the MTD question disappears.
- You apply for gross payment status. The compliance test is what fails most applications, and since April 2026 HMRC can revoke status immediately where a contractor knew or should have known of fraudulent supply-chain connections, with a five-year reapplication ban.
- You register for VAT. The domestic reverse charge then applies to most of your CIS invoices, with the end-user exception and the 5% de minimis to judge on each job.
- Your records slipped. If the last two years were reconstructed in January from bank statements, quarterly deadlines will find that out fast. Fixing the record is a one-off job worth paying for even if you then self-serve.
Getting the MTD decision right for your situation
MTD for Income Tax is a filing mechanism, and a subcontractor with one clean income stream can run it alone with free or low-cost software. The decision only becomes finely balanced once CIS reconciliation, expense completeness, gross payment status or a second role as a contractor enters the picture, because those are judgement questions that software does not answer. The right test is your own numbers: hours released, refund difference, penalty exposure.
Two supporting reads will sharpen the answer. Our guide to Making Tax Digital and CIS covers the gross income threshold trap in detail, and CIS record keeping sets out what your digital records need to hold before the first quarterly update is due.
If you want the decision tested against your actual figures rather than a general rule, our CIS accounting services page sets out the scope of what a construction-specialist firm covers, from quarterly MTD submissions through to gross payment status and EPS reclaims.