2026/27 Tax Deadlines Calendar: Every Date UK Small Business Owners Need to Know

Staying on top of tax deadlines is more than just a matter of compliance; it is a vital part of managing your business's cash flow and avoiding unnecessary penalties. As we move into the 2026/27 tax year, the landscape for UK small business owners is shifting significantly, primarily due to the rollout of Making Tax Digital for Income Tax Self Assessment (MTD ITSA).

Whether you are a seasoned sole trader, a growing limited company, or a new startup, keeping a close eye on the calendar is essential. Missing a single date can result in automatic fines that eat into your hard-earned profits. This guide provides a comprehensive breakdown of the key tax dates for the 2026/27 period, including the new quarterly requirements that many businesses will face for the first time.

The Big Change: MTD for ITSA is Here

The 2026/27 tax year marks a historic milestone for the UK tax system. From 6 April 2026, self-employed individuals and landlords with a qualifying income of over £50,000 are legally required to follow Making Tax Digital rules for Income Tax.

This means that instead of filing one annual tax return, many business owners must now:

• Keep digital records of all business transactions.

• Use MTD-compatible software to send quarterly updates to HMRC.

• Provide a final declaration at the end of the tax year.

If your income is between £30,000 and £50,000, you have until April 2027 before these rules become mandatory, but many are choosing to join early to streamline their bookkeeping. For those impacted this year, the calendar below is your new roadmap.

Your 2026/27 Tax Calendar: Month-by-Month

To help you stay organized, we have broken down the year into the most critical dates. While some of these refer to the previous tax year (2025/26) being filed and paid during this window, they are the dates you must mark in your 2026/27 diary.

July 2026: The Second Payment on Account

Date: 31 July 2026 If you are registered for Self Assessment and your tax bill was more than £1,000 in the previous year, you likely have to make "payments on account." The 31st of July is the deadline for your second payment on account for the 2025/26 tax year. This is a crucial date for cash flow, as it often catches business owners off guard during the summer months.

August 2026: The First MTD Quarterly Update

Date: 7 August 2026 For those mandated into MTD ITSA (earning over £50,000), this is a major new deadline. You must submit your first quarterly update covering the period from 6 April to 5 July 2026. This update is a summary of your income and expenses, and while no tax is typically paid at this specific moment, the submission itself is mandatory. For a closer look at what this deadline means, read 7 August 2026: Your First MTD Quarterly Deadline is Coming.

October 2026: Registration and Paper Returns

Date: 5 October 2026 If you started a new business or became a landlord during the 2025/26 tax year, this is the deadline to register for Self Assessment with HMRC. If you fail to register by this date, you could face "failure to notify" penalties.

Date: 31 October 2026 For the very few business owners who still file paper tax returns, this is the hard deadline for the 2025/26 tax year. However, if you are moving toward MTD, you will likely be filing digitally, which gives you more time.

November 2026: Second MTD Quarterly Update

Date: 7 November 2026 The second quarterly update for MTD ITSA is due. This covers the period from 6 July to 5 October 2026. Keeping your records up to date monthly makes this a five-minute job rather than a week-long stress.

January 2027: The Big Deadline

Date: 31 January 2027 This remains the busiest day in the UK tax calendar. On this date, several things are due:

1. Online Tax Return: You must file your 2025/26 Self Assessment return online.

2. Balancing Payment: You must pay any remaining tax owed for the 2025/26 year.

3. First Payment on Account: You must pay the first installment for the 2026/27 tax year.

Failure to meet these deadlines results in an immediate £100 fine, with interest and further penalties added the longer the delay. If you need help with this, it is worth consulting a Self Assessment accountant well in advance.

February 2027: Third MTD Quarterly Update

Date: 7 February 2027 The third MTD update is due, covering the period from 6 October 2026 to 5 January 2027. By now, the rhythm of quarterly reporting should be feeling more natural.

April 2027: The Tax Year Ends

Date: 5 April 2027 The 2026/27 tax year officially ends. This is your last chance to utilize tax allowances, such as ISA limits or pension contributions, to reduce your overall tax liability for the year.

May 2027: Final MTD Quarterly Update

Date: 7 May 2027 The fourth and final update for the 2026/27 tax year is due. Following this, you will work toward your "Final Declaration" and "End of Period Statement," which are due by January 2028.

Deadlines for Limited Companies

If you operate as a Limited Company, your deadlines are not tied to the 6 April tax year but rather to your company's own financial year-end. However, there are two general rules to remember:

• Corporation Tax Payment: Usually due 9 months and 1 day after your accounting period ends.

• Company Tax Return (CT600): Due 12 months after your accounting period ends.

For example, if your year-end is 31 December, your tax payment is due by 1 October the following year. If you find these overlapping dates confusing, matching with a limited company accountant can ensure you never miss a filing.

VAT and Payroll Deadlines

While income tax gets the most attention, small businesses with employees or high turnover have additional monthly and quarterly obligations:

• VAT Returns: Usually due one calendar month and seven days after the end of your VAT quarter. If you need specific advice, our VAT accountants can help manage these rolling deadlines.

• PAYE/National Insurance: If you have employees, these payments must reach HMRC by the 22nd of each month (or the 19th if paying by post).

Why You Shouldn't Wait Until the Deadline

The most common mistake small business owners make is waiting until the week of a deadline to gather their documents. This leads to errors, missed tax-saving opportunities, and unnecessary stress. For a practical checklist, see MTD Countdown: 5 Things to Check Before the August 7th Deadline.

With the introduction of MTD, the "January panic" is being replaced by a need for consistent, year-round record-keeping. Using an accountant is no longer just about filing a return at the end of the year; it's about having a partner who ensures your digital records are accurate every quarter.

At Accountant Search, we specialize in connecting SME businesses with the right tax professionals. Whether you are looking for bookkeeping services to handle your MTD updates or a tax preparation expert to optimize your annual return, we can match you with an accountant who understands your specific industry.

Conclusion

The 2026/27 tax year is a period of transition. Between the traditional Self Assessment dates and the new MTD requirements, there are more deadlines than ever to track. By marking these dates in your calendar today, you can protect your business from penalties and focus on what you do best: growing your company. If you are also reviewing your options, our guide to finding the right accountant for your business is a useful next read.

Don't wait for the fines to arrive. Get ahead of the game by finding a local expert. Whether you need accountants in London, accountants in Ilford, or anywhere else across the UK, we are here to help you find the perfect match.