7 Mistakes You're Making with MTD 2026 (and How to Avoid Huge Fines)

Let’s be honest: nobody starts a business because they love paperwork. You started yours to build something, help people, or finally be your own boss. But in the background, the UK tax system is going through its biggest shake-up in decades.

If you’re a sole trader or a landlord, the mtd start date 2026 is likely already on your radar: or at least, it should be. From 6 April 2026, Making Tax Digital (MTD) for Income Tax Self Assessment (ITSA) becomes mandatory for many.

It sounds technical, and frankly, a bit boring. But getting it wrong isn't just a headache; it's expensive. HMRC is introducing a points-based system that could see you slapped with £200 fines for simple mistakes.

At Accountant Search, we’ve seen plenty of SMEs get caught out by changing regulations. To help you stay ahead of the game, here are the seven biggest mistakes people are making with MTD 2026 and: more importantly: how you can avoid them.

1. The £50,000 Blind Spot

The most common mistake right now is thinking, "This doesn't apply to me yet."

The mtd start date 2026 specifically targets individuals, sole traders, and landlords with a combined qualifying income of over £50,000.

Here is the kicker: HMRC looks at your income from the 2024-25 tax year to decide if you need to join in April 2026. If you wait until 2026 to check your old records, you might find you’ve missed the boat on preparation.

How to avoid it: Check your total turnover (not profit, but total income) for the current tax year. If it’s hovering near £50k, start acting as if you are already in the MTD loop. Remember, the threshold drops to £30,000 in April 2027, so even if you're safe now, you won't be for long.

2. Thinking Excel is "Digital Enough"

We love a good spreadsheet. They are flexible, free, and familiar. But come April 2026, a "naked" Excel spreadsheet won't cut it.

MTD requires "digital links." This means your data must flow from your records to HMRC without any manual "copy and pasting." If you’re typing totals from a spreadsheet into a government portal, you are breaking the rules.

How to avoid it: You don't necessarily have to abandon Excel if you truly love it, but you will need bridging software. This is a digital tool that "talks" to your spreadsheet and "talks" to HMRC, creating that mandatory digital link. However, most businesses find it's actually easier to move to a cloud-based system like Xero or QuickBooks.

3. Leaving the Software Hunt Until March 2026

Think back to when the last major Windows update happened, or when everyone tried to buy a turkey on Christmas Eve. High demand leads to stress and technical glitches.

If you wait until the month before the mtd start date 2026 to choose your software, you’ll be competing with hundreds of thousands of other business owners. You won't have time to learn the system, and you might find that the best accountants are already "fully booked" helping other proactive clients.

How to avoid it: Start testing software now. Many providers offer free trials. By getting your digital record-keeping sorted in 2024 or 2025, the transition in 2026 will be a non-event rather than a crisis.

4. Confusing "Updates" with "Tax Payments"

Under MTD for ITSA, you have to send quarterly updates to HMRC.

• Quarter 1: Due 7 August

• Quarter 2: Due 7 November

• Quarter 3: Due 7 February

• Quarter 4: Due 7 May

A big mistake is thinking that because you are filing four times a year, you have to pay tax four times a year. This is causing a lot of unnecessary cash-flow panic.

How to avoid it: Don't panic. The quarterly updates are just summaries of your income and expenses so HMRC (and you) have a real-time view of what you might owe. Your actual tax payment deadlines generally remain the same: 31 January and 31 July.

5. Missing the "Final Declaration"

This is the "Boss Level" of MTD mistakes.

Because you’ve been sending quarterly updates, you might think you’re done. But you’re not. You still have to submit a Final Declaration by 31 January following the tax year. This is where you claim reliefs, confirm the final figures, and "sign off" on your tax for the year.

HMRC has signaled a "soft landing" for quarterly update penalties in the first year, but they have been very clear: there is no soft landing for the Final Declaration. If this is late, the fines start immediately.

How to avoid it: Treat the 31 January deadline with the same respect you always have. Your MTD software will help you pull your four quarterly updates together into this final report, making it much faster than the old manual way.

6. The "Exemption Assumption"

Some people assume they are "digitally excluded" because they live in a rural area with bad internet or aren't comfortable with computers.

HMRC does offer exemptions, but they are not automatic. If you just stop filing and hope for the best, you’ll be hit with the points-based penalty system.

How to avoid it: If you truly believe you cannot comply with MTD due to age, disability, location, or religious grounds, you must apply for an exemption through GOV.UK. Do this well in advance of April 2026.

7. Going It Alone

The biggest mistake of all? Trying to navigate the mtd start date 2026 entirely on your own.

MTD isn't just about clicking a button; it's about ensuring your transactions are categorized correctly. If you mislabel an expense in your software, that error is reported to HMRC four times a year. By the time you reach your Final Declaration, you could have a mess that takes an accountant days (and a lot of your money) to fix.

How to avoid it: Get an MTD-ready accountant in your corner. They can help you set up the right software, ensure your digital links are compliant, and handle the quarterly submissions so you can focus on running your business.

Practical Checklist: How to Avoid the £200 Fines

HMRC’s new points system is simple: miss a deadline, get a point. Reach 4 points (for quarterly filers), and you get a £200 fine. Every miss after that is another £200.

• Step 1: Confirm your income. Was your 2024-25 turnover over £50k?

• Step 2: Get software. Don't wait; digital record-keeping is a legal requirement from day one.

• Step 3: Set reminders. Quarterly updates are due on the 7th of the month (August, November, February, May).

• Step 4: Keep digital receipts. Use apps like Dext or Hubdoc to snap photos of receipts so they are digitally linked to your software.

• Step 5: Connect with a pro. Use a service like Accountant Search to find a local expert who understands MTD for ITSA.

The mtd start date 2026 doesn't have to be a nightmare. With the right tools and a bit of early preparation, you can turn a complicated tax change into a streamlined digital process that actually gives you more clarity on your business finances.

Need help finding an accountant who specializes in MTD? We can match you with the perfect firm for your SME.

Our Location: Office 107, The Shed, Sergeants Yard, Bordon, Hampshire, GU35 0DJ.

Sam is a regular contributor to the Accountant Search blog, focusing on helping UK small businesses navigate the complexities of tax digitalisations and growth.