Five MTD Mistakes That Could Cost You — And How to Avoid Every One of Them

Making Tax Digital for Income Tax is, in principle, straightforward. Digital records, quarterly updates, an end-of-year declaration. The technology exists. The software is accessible. The support is available.

And yet, across our work with self-employed clients preparing for and transitioning into MTD, we see the same mistakes appearing time and again. Not because people are careless — but because MTD introduces a set of requirements that differ enough from the old Self Assessment world that assumptions about what’s allowed often turn out to be wrong.

This blog identifies the five most significant mistakes we see self-employed people make with MTD, explains why they matter, and gives you a clear picture of what to do instead. The good news is that every one of these mistakes is entirely preventable — and none requires anything complicated to fix.

Why Getting MTD Right Matters

HMRC’s penalty framework for MTD non-compliance is based on a points system. Every late or missing submission earns penalty points, and once a threshold is crossed, financial penalties follow. Unlike the old annual tax return — where one missed deadline triggered one fine — the quarterly nature of MTD means multiple compliance events per year, each of which can generate points.

Beyond penalties, there’s a more practical concern: MTD is designed to give HMRC real-time visibility of your income. Errors in quarterly updates can lead to incorrect tax estimates, unexpected underpayments at year-end, and, in more serious cases, HMRC enquiries. Getting the foundation right matters.

Mistake 1: Leaving Preparation Until the Deadline Is Imminent

This is, consistently, the most common MTD mistake we see — and the one with the widest-ranging consequences. Self-employed people see their MTD start date on the horizon and assume they have plenty of time. Then, as the deadline approaches, they discover that setting up software, migrating records, establishing quarterly habits, and connecting to HMRC all take longer than anticipated.

The April 2026 cohort (income over £50,000) is already mandated. Those in the £30,000 bracket have until April 2027, and the £20,000 bracket until April 2028. These dates may feel distant — but the preparation window is shorter than it appears, particularly if you’re starting from paper records or manual spreadsheets.

Leaving preparation to the final weeks means rushed software setup, incomplete records, and first quarterly submissions made under pressure. It also means missing the opportunity to get comfortable with the process before it’s mandatory.

💡 Crew Insight In our experience, early preparation reduces the stress of MTD to almost nothing. Clients who set up six to twelve months ahead of their start date typically describe their first quarterly submission as ‘surprisingly quick’. Those who start in the month before their deadline describe something rather different. The investment of time upfront pays back many times over.

Mistake 2: Assuming Existing Software or Spreadsheets Are MTD-Compliant

MTD has a firm requirement: submissions must be made through HMRC-recognised software. Not all accounting software qualifies. Older platforms, generic bookkeeping tools, and spreadsheets — even sophisticated ones — do not meet the standard unless they have specific MTD functionality and HMRC approval.

Spreadsheets occupy a particularly grey area. They’re not outright banned — a spreadsheet can be part of an MTD-compliant setup if it’s connected via a digital link to bridging software that submits to HMRC. But the bridging software adds a layer of complexity that most self-employed people find more trouble than it’s worth. For the vast majority, switching to a purpose-built MTD platform is the simpler, safer, and ultimately more efficient choice.

The two platforms we work with and recommend are Xero and FreeAgent. Both are HMRC-recognised, fully MTD-compliant, and designed to handle quarterly submissions with minimal friction. As an Accounting Crew client, you access 20% off Xero and 50% off FreeAgent.

💡 Crew Insight The question of whether to use bridging software or purpose-built MTD software comes up regularly. Our position is clear: unless you have a specific reason to retain a spreadsheet-based system, moving to Xero or FreeAgent produces a better outcome — simpler compliance, less manual work, and a cleaner financial record. The discount we offer makes the cost a non-issue for most clients.

Mistake 3: Breaking the Digital Link Requirement

This is a more technical mistake, but one with real compliance implications. MTD requires that data flows digitally from its source through to your submission — without any manual re-entry. This principle, known as a ‘digital link’, means that copying figures by hand from one system to another breaks the compliance chain.

The most common version of this mistake involves spreadsheets: a self-employed person captures their income and expenses on a spreadsheet, then manually types those figures into a submission tool. That manual transfer is a broken digital link — and it violates MTD’s record-keeping requirements.

If you’re using purpose-built software like Xero or FreeAgent, this isn’t an issue — the data flows from your records directly to the HMRC submission within the same system. But if you’re operating a hybrid approach involving spreadsheets, it’s essential to check that your data transfer is genuinely digital, not manual.

Mistake 4: Treating Quarterly Updates as Mini Tax Returns

There’s a widespread misunderstanding that quarterly MTD updates are the equivalent of quarterly tax returns — with all the scrutiny, complexity, and preparation that a full return implies. They’re not.

Quarterly updates are summaries of your income and expenses for that period. They don’t need to be perfect at the point of submission — adjustments can be made in later quarters or in the final end-of-year declaration. They don’t trigger an immediate tax payment. And they don’t require the level of detail or preparation that the annual Self Assessment used to demand.

The practical implication is that the bar for a quarterly submission is lower than most people expect. The discipline required is in keeping records up to date throughout the quarter — so that when submission time comes, the numbers are already there and the process is genuinely quick.

💡 Crew Insight We often describe the quarterly update as a ‘temperature check’ rather than a tax return. Its purpose is to give HMRC a running picture of your finances throughout the year. The final declaration is where things are formally confirmed and adjusted. Understanding this distinction tends to take a significant amount of stress out of the MTD process.

Mistake 5: Not Considering Income Thresholds Correctly

The income threshold for MTD is based on your total gross income from self-employment and rental property — combined, and before expenses. This catches people out in two directions.

First, some self-employed people don’t realise that rental income counts towards the threshold. A sole trader earning £35,000 from their business who also has £18,000 of rental income has combined gross income of £53,000 — placing them in the April 2026 cohort, not April 2027 as they might have assumed.

Second, income fluctuates. Someone whose income sits just below a threshold in one year may cross it the next — and because MTD start dates are based on the income in the prior tax year, the mandate can arrive with less warning than expected. Monitoring your income position against the thresholds is a useful annual exercise.

💡 Crew Insight We recommend that any self-employed person with income that could plausibly cross a threshold — particularly those sitting between £18,000 and £55,000 — should check their combined income against the MTD thresholds each year. This is something we do as a matter of course with our clients, but if you’re managing this yourself, it’s worth building it into your year-end review.

The Accounting Crew’s Perspective

The five mistakes outlined above are not edge cases — they’re patterns we see repeatedly. And in almost every case, they arise from the same root cause: not having the right information and support at the right time.

MTD is a genuine change to how self-employed people report their income. Getting it right requires understanding the rules, choosing appropriate software, and establishing new quarterly habits. None of that is particularly difficult — but it does require some upfront investment of time and attention.

Our role is to make that investment as small as possible for our clients. We handle the software setup, the HMRC connection, and the quarterly submissions. Our clients keep their records current throughout the quarter — and the process, once established, is significantly less onerous than the old annual approach.

Conclusion

Making Tax Digital doesn’t have to be complicated or stressful. But like any significant change to a compliance process, it does reward preparation and penalise assumptions. The five mistakes outlined in this blog are entirely preventable — and avoiding them starts with understanding what MTD actually requires and getting the right support in place early.

Whether you’re already mandated or preparing for a future deadline, the most valuable thing you can do right now is get a clear picture of your current position and what you need to do next.

Frequently Asked Questions

What happens if I miss an MTD quarterly update?

HMRC operates a points-based penalty system for MTD. Each missed or late submission earns a penalty point. Once you accumulate enough points (the threshold depends on your submission frequency), a financial penalty is charged. Staying on top of quarterly submissions avoids this entirely.

Are spreadsheets allowed under MTD?

Spreadsheets can be part of an MTD-compliant setup if they connect digitally to HMRC-recognised bridging software — with no manual data transfer at any point. In practice, most self-employed people find purpose-built software like Xero or FreeAgent simpler and more reliable.

What is a digital link and why does it matter?

A digital link is an unbroken, automated flow of data from your records to your HMRC submission. Manually re-entering figures from one system to another breaks the digital link and violates MTD’s record-keeping requirements. Purpose-built MTD software handles this automatically.

Do rental income and self-employment income both count towards the MTD threshold?

Yes — the MTD threshold is based on combined gross income from self-employment and property rental, before expenses. If your combined income exceeds £50,000 (already), £30,000 (from April 2027), or £20,000 (from April 2028), you are in scope.

How can The Accounting Crew help me avoid MTD mistakes?

We handle the full MTD setup for our clients — software selection and configuration, HMRC connection, and ongoing quarterly submissions support. We also check threshold positions annually so clients know where they stand. Book a free discovery call to find out more.

If any of the five mistakes in this blog sound familiar — or if you’re simply not sure whether your current MTD approach is fully compliant — the most useful step is a clear conversation about where you stand.

Ready to Take Control of Your Finances? The Accounting Crew takes care of MTD compliance from end to end — setup, quarterly submissions, and year-end declarations. We work with self-employed people and contractors across all income levels, and we make the process as straightforward as it should be. Book your free discovery call today. 👉  Book your free discovery call at theaccountingcrew.co.uk/book-a-free-call/