MTD for the Self-Employed: Common Mistakes and How to Avoid Them

Making Tax Digital is new territory for most self-employed people. Even those who have filed Self Assessment for years are finding the shift to quarterly digital reporting requires different habits. Here are the most common mistakes sole traders are making with MTD — and practical advice on how to avoid every one of them.

Mistake 1: Confusing Gross Income with Profit

This is the single most common error. Many sole traders assume the £50,000 MTD threshold refers to their profit — what they take home after expenses. It does not. The threshold is based on gross income, which is your total business turnover before deducting anything.

A plumber billing £55,000 per year but spending £15,000 on materials, van costs, and insurance has a profit of £40,000. But their gross income is £55,000, which puts them firmly above the MTD threshold.

How to avoid it: Check your last Self Assessment tax return. Look at your turnover figure (box 15 on the self-employment pages), not your profit figure. If it exceeds £50,000, you need to comply from April 2026.

Mistake 2: Waiting Until the Last Minute

Some sole traders are treating MTD like the annual Self Assessment rush — planning to sort everything out just before the first deadline. This is a recipe for stress and errors.

MTD requires you to have compatible software set up, bank feeds connected, and records in order from the start of the tax year. If you wait until August 2026 to set things up, you will be scrambling to record three months of transactions retrospectively.

How to avoid it: Set up your MTD software now. Connect your bank account, start categorising transactions, and get comfortable with the system before April 2026. Even a few weeks of practice will make a significant difference.

Mistake 3: Using Software That Is Not MTD-Compatible

Not all accounting or bookkeeping software can submit MTD quarterly updates. Some popular tools may handle VAT MTD but not Income Tax MTD. Others are simply not on HMRC's approved list.

How to avoid it: Check HMRC's official list of MTD-compatible software for Income Tax. Ensure your chosen software explicitly supports MTD ITSA, not just MTD for VAT. Accounted is fully MTD ITSA compatible and designed specifically for UK sole traders.

Mistake 4: Not Separating Business and Personal Transactions

If you use the same bank account for business and personal spending, every personal transaction will be imported into your MTD software alongside your business ones. This creates extra work and increases the risk of accidentally including personal expenses in your business figures.

How to avoid it: Use a separate business bank account. This is not a legal requirement for sole traders, but it makes MTD compliance dramatically easier. If you absolutely cannot separate accounts, be meticulous about tagging personal transactions as excluded.

Mistake 5: Ignoring Cash Transactions

Bank feeds are excellent for capturing card payments and bank transfers, but they cannot capture cash transactions. If a customer pays you in cash, or you buy materials with cash, these transactions need to be entered manually.

Many sole traders are relying entirely on bank feeds and forgetting about their cash transactions, which means their quarterly updates are incomplete.

How to avoid it: Get into the habit of recording cash transactions immediately. Snap a photo of the receipt via WhatsApp to Accounted, and Penny will create the transaction for you. Alternatively, set aside time each week to enter any cash items manually.

Mistake 6: Miscategorising Expenses

Under MTD, expenses must be categorised correctly — they feed into your quarterly updates and ultimately your tax calculation. Common categorisation errors include:

• Putting meals with clients under "subsistence" instead of "business entertaining" (which is not tax deductible)
• Categorising a new laptop as "office supplies" instead of "equipment" (which may qualify for capital allowances rather than being an immediate expense)
• Failing to apportion mixed-use expenses like phone bills or home office costs

How to avoid it: Familiarise yourself with the standard expense categories and which expenses fall where. If your software uses AI categorisation, review the suggestions rather than blindly accepting them. Accounted's Penny explains why she has categorised each expense a certain way, so you can learn as you go.

Mistake 7: Forgetting the Final Declaration

MTD quarterly updates are not the end of the story. After the tax year ends, you must file a final declaration by 31 January. This replaces your Self Assessment tax return and confirms your full-year figures.

Some sole traders are assuming that four quarterly updates is all they need to do, and are planning to skip the final declaration.

How to avoid it: Mark 31 January in your calendar as the final declaration deadline. Your software should prompt you, but do not rely on it alone. The final declaration is where adjustments, capital allowances, and other year-end items are included.

Mistake 8: Not Backing Up Records

Digital records can be lost if your computer fails, your software provider has issues, or you accidentally delete data. Under MTD, you are required to keep records for at least five years after the 31 January filing deadline.

How to avoid it: Use cloud-based MTD software (like Accounted), which automatically backs up your data. If you use desktop software, ensure you have regular backups to an external drive or cloud storage.

Mistake 9: Treating Quarterly Updates as Optional

Some sole traders have heard that MTD penalties will be lenient initially and are planning to skip quarters or submit late without worrying about consequences.

While HMRC has said it will take a "light touch" approach initially, the points-based penalty system is real. Each late quarterly submission earns a penalty point, and once you hit the threshold (4 points), every subsequent late submission costs £200.

How to avoid it: Treat every quarterly deadline as non-negotiable. If your records are up to date, submission takes minutes. There is no good reason to miss a deadline.

Mistake 10: Not Using Bank Feeds

Some sole traders are planning to type every transaction into their MTD software manually. While this is technically compliant, it is enormously time-consuming and error-prone. Manual entry is the number one cause of missing transactions and incorrect figures.

How to avoid it: Connect your business bank account to your MTD software using Open Banking. Transactions are imported automatically, typically within 24 hours. You just need to categorise them, which AI-powered software does for you.

Mistake 11: Ignoring Property Income

If you have rental income from property alongside your self-employment income, both count towards the £50,000 threshold and both must be reported through MTD.

Some sole traders who also earn rental income are focusing only on their self-employment figures and forgetting that their property income pushes them over the threshold.

How to avoid it: Add up all your self-employment and property income. If the combined gross figure exceeds £50,000, you need to report everything through MTD.

Mistake 12: Not Involving Your Accountant Early Enough

If you use an accountant, they need to be part of your MTD setup. Many accountants are also adapting to MTD, and the earlier you coordinate with them, the smoother the transition will be.

How to avoid it: Talk to your accountant about MTD now. Agree on who will manage the software, who will review quarterly updates, and how you will share access. If your accountant recommends specific software, consider their suggestion — it helps if you are both using the same platform.

The Bottom Line

Most MTD mistakes come down to either misunderstanding the requirements or leaving preparation too late. The good news is that all of these errors are avoidable with a bit of planning and the right software.

Stop dreading your Self Assessment. Accounted tracks everything throughout the year so January is just a click, not a crisis. Try it free.