7 Mistakes You’re Making with the 2026 HMRC Tax Updates (and How to Fix Them)

by Ariful | Mar 17, 2026 | UK Updates

1. Missing the MTD for Income Tax Deadline

The biggest shift this year is the mandatory rollout of Making Tax Digital (MTD) for Income Tax Self-Assessment (ITSA). From 6 April 2026, if you are a sole trader or a landlord with a total qualifying income over £50,000, the old way of filing once a year is dead.

The Mistake: Thinking you can still submit a single annual return through the HMRC portal in January.
The Fix: You must register for MTD for ITSA immediately. Under the new rules, you are required to keep digital records of every transaction and submit quarterly updates to HMRC using compatible software. Waiting until the end of the tax year will result in a compliance nightmare.

Registering now allows us to integrate your daily bookkeeping into a compliant flow. This ensures your data is “HMRC-ready” every single day, rather than scrambling every three months. You can learn more about why hiring e-commerce accountants makes your life easier when navigating these digital shifts.

2. Underestimating the 2% Dividend Tax Hike

For many directors of UK Limited Companies, dividends have long been a tax-efficient way to extract profit. However, as of April 2026, those rates are climbing.

The Mistake: Failing to adjust your extraction strategy to account for the new rates.
The Fix: Understand the numbers. From April 2026, dividend tax rates are rising by 2%.

• Basic rate taxpayers will now pay 10.75%.
• Higher rate taxpayers will now pay 35.75%.

If you are an investor or a business owner relying on these payouts, you need to calculate the impact on your net take-home pay today. While we focus on the operational filing and calculation of these taxes, you should ensure your internal accounts reflect these higher liabilities so you aren’t hit with a surprise bill next year.

3. Miscalculating Capital Gains on Business Disposals

If you were planning to sell your business or significant assets this year, the math just changed. The tax relief for entrepreneurs is becoming less generous.

The Mistake: Assuming your Capital Gains Tax (CGT) rate remains at 14% for qualifying disposals.
The Fix: Prepare for the increase to 18%. The rate for those claiming Business Asset Disposal Relief (BADR) or Investors’ Relief is stepping up.

If you are in the middle of a sale, the timing is critical. To stay compliant and ensure you are calculating your liabilities correctly, you must use precise data. Small errors in CGT calculations are a magnet for audits. Check our guide on how to avoid HMRC self-assessment tax investigations to see how clean reporting keeps the taxman away.

4. Ignoring the New £2.5 Million Inheritance Tax Cap

This update hits family-owned businesses and agricultural landowners the hardest. For years, Agricultural Property Relief (APR) and Business Property Relief (BPR) allowed many to pass on assets with 100% relief.

The Mistake: Relying on outdated estate planning that assumes 100% relief on all business assets.
The Fix: Audit your asset value now. From 6 April 2026, APR and BPR are capped at a combined £2.5 million. Anything above this threshold only receives 50% relief. Furthermore, AIM shares: previously a staple for IHT planning: have had their relief slashed to 50% across the board.

Because Sterlinx Global provides end-to-end compliance, we ensure that your year-end accounts accurately reflect the value of these assets, providing the data needed for your estate considerations.

5. Working with Unregistered Tax Advisers

HMRC is cracking down on who can represent you. This is a move toward professionalizing the industry and reducing “ghost” preparers who submit inaccurate claims.

The Mistake: Continuing to use a “friend of a friend” or an informal preparer who isn’t officially registered with HMRC.
The Fix: By May 2026, all tax advisers interacting with HMRC on behalf of clients must be registered.

As a Global Tax Compliance Suite, Sterlinx Global is fully integrated into the regulatory framework. When we handle your VAT, bookkeeping, and year-end accounts, you are backed by a structured, professional entity. This registration requirement is designed to protect you; don’t risk your business by using an adviser who hides from the regulator.

6. Treating Cross-Border E-commerce like Domestic Retail

If you sell on Amazon, Shopify, or eBay, the 2026 updates place a higher burden on transaction-level reporting. HMRC is increasingly using data-sharing agreements with digital platforms to cross-reference your reported income.

The Mistake: Not reconciling global sales with UK VAT requirements and the new MTD quarterly updates.
The Fix: Implement a daily compliance model. E-commerce moves too fast for monthly or quarterly “catch-up” bookkeeping. You need to ensure that your VAT calculations: especially if you are selling into Europe or the US: are handled in real-time.

For those expanding into Europe, the rules are even tighter. Whether you are looking at specifics of French VAT for e-commerce or trying to stay compliant with France’s VAT e-invoicing rules, the data must be seamless. Use our VAT calculator to keep your pricing compliant across borders.

7. The “January 31st” Procrastination Habit

The tradition of the “January tax rush” is officially a liability. With the 2026 updates, the “once-a-year” mindset will lead to automatic penalties.

The Mistake: Waiting until the end of the year to organize your receipts and invoices.
The Fix: Move to a “Daily Compliance” mindset. Since MTD for ITSA requires quarterly updates, your bookkeeping must be current every single month.

Don’t worry; this shift actually benefits you. By having a clear view of your tax liability throughout the year, you can manage cash flow more effectively. You won’t be surprised by a massive tax bill in January because you: and we: will have seen it coming months in advance.

7 Mistakes You’re Making with UK Limited Company Tax Filings (and How to Fix Them)

by Ariful | Mar 17, 2026 | UK Updates

Running a UK Limited Company comes with a specific set of administrative hurdles. Whether you are a local entrepreneur or an international seller who utilized company formation for non-UK residents, the responsibility of Corporation Tax compliance sits squarely on your shoulders.

As of March 2026, HMRC has increased its focus on digital record-keeping and data cross-referencing. For ecommerce brands and fast-growing SMEs, a single oversight in your CT600 (Corporation Tax Return) can lead to more than just a slap on the wrist, it can result in significant financial penalties and unnecessary tax bills.

At Sterlinx Global Ltd, we see these errors daily. Here are the seven most common mistakes directors make with their UK tax filings and, more importantly, how you can fix them before the deadline hits.

1. Confusing the Filing Deadline with the Payment Deadline

This is the “silent killer” for many new business owners. In the UK, the timeline for your accounts and your tax return does not always follow a simple logic.

• The Mistake: Many directors assume they have 12 months to pay their tax because they have 12 months to file their CT600 return.
• The Reality: For most companies with taxable profits up to £1.5 million, the deadline to pay your Corporation Tax is usually 9 months and 1 day after the end of your accounting period. However, the deadline to file your CT600 is 12 months after the end of that period.

The Fix: Set two separate calendar alerts. If your year-end is 31st December, your payment is due by 1st October the following year, even if you don’t submit the paperwork until December. Paying late triggers automatic interest charges from HMRC, even if it was an honest mistake.

2. Incorrect Accounting Period Dates (Especially in Year One)

If you have just started your journey, your first “year” of trading rarely fits into a neat 12-month window.

• The Mistake: Entering the wrong start or end dates on your CT600. This is common when a company’s first accounting period is longer than 12 months (which happens often when you register a company and choose a specific year-end).
• The Reality: A Corporation Tax return cannot cover a period longer than 12 months. If your first set of accounts covers 13 months, you actually need to file two separate tax returns: one for the first 12 months and one for the remaining month.

The Fix: Check your Accounting Reference Date (ARD) on Companies House. Before you start your filing, verify the exact dates HMRC expects. This is why we recommend using UK tax tips to run your business accounting to ensure your internal records match the official registry.

3. Treating Depreciation as a Tax-Deductible Expense

In your profit and loss statement, depreciation is a standard accounting entry to show how your assets (like laptops or machinery) lose value over time.

• The Mistake: Assuming that because depreciation reduces your “accounting profit,” it also reduces your “taxable profit.”
• The Reality: HMRC does not allow depreciation as a tax-deductible expense. Instead, they use a system called Capital Allowances.

The Fix: You must “add back” depreciation to your profit and then claim Capital Allowances instead. In 2026, the Annual Investment Allowance (AIA) remains a powerful tool, allowing most businesses to claim 100% of the cost of qualifying plant and machinery (up to £1 million) in the year of purchase. If you bought £5,000 worth of hardware for your ecommerce operations, make sure you claim the AIA to wipe that cost off your taxable profit immediately.

4. Including Non-Deductible “Business” Expenses

It is a common misconception that if a company pays for something, it is automatically a business expense.

• The Mistake: Claiming for client entertainment, personal travel, or regulatory fines.
• The Reality: HMRC is very strict. “Business entertaining” (taking a client to lunch) is almost never tax-deductible. Neither are parking fines or certain legal costs related to capital structures.
• Ecommerce Impact: For sellers, this often extends to personal subscriptions that aren’t “wholly and exclusively” for the business.

The Fix: Separate your expenses into “allowable” and “disallowable” categories in your bookkeeping software (like Xero or QuickBooks) throughout the year. When we handle your compliance at Sterlinx Global, we automatically filter these out to ensure your CT600 is compliant and doesn’t trigger an HMRC enquiry.

5. Failing to Report Global Income or “Other” Revenue

For businesses involved in Amazon Pan-European VAT or international sales, income streams can get messy.

• The Mistake: Only reporting UK-based sales or forgetting about secondary income like bank interest, rental income from company property, or profit from the sale of assets (Capital Gains).
• The Reality: A UK Limited Company is taxed on its worldwide profits. Even if the money stays in a foreign currency account or a digital wallet like Wise or Payoneer, it must be reported.

The Fix: Perform a full bank reconciliation across all platforms. Ensure your “Total Income” figure includes every penny the company received, regardless of where the customer was located or which currency they paid in.

6. Poor Record-Keeping and “The Shoebox Method”

In the age of Making Tax Digital (MTD), the “shoebox full of receipts” is not just inefficient, it’s a compliance risk.

• The Mistake: Relying on manual spreadsheets or waiting until the end of the year to “sort out the books.”
• The Reality: Disorganised records lead to duplicate entries, missing VAT reclaim opportunities, and incorrect opening balances. If your opening balance doesn’t match the closing balance of the previous year, HMRC’s systems will flag your return for review.

The Fix: Move to a cloud-based accounting system immediately. Link your business bank feeds so transactions are pulled in daily. At Sterlinx Global, we function as your data-driven compliance partner; you provide the digital data, and we ensure the bookkeeping is tax-ready every single day.

7. Submitting Without an iXBRL Format Review

HMRC requires all company tax returns and accounts to be submitted in a specific digital language called iXBRL (Inline eXtensible Business Reporting Language).

• The Mistake: Trying to upload a standard PDF or a Word document of your accounts to the HMRC portal.
• The Reality: HMRC’s software will reject non-iXBRL files. Furthermore, if the “tags” in the iXBRL file are incorrect, your tax calculations might be misinterpreted by HMRC’s automated systems.

The Fix: Don’t DIY your filing if you aren’t using professional tax software. Most “off-the-shelf” consumer tools are fine for basic bookkeeping but may not produce iXBRL-compliant submissions. If you’re submitting to Companies House and HMRC simultaneously, a specialist accountant or compliance platform is non-negotiable.