The start of a new tax year on 6 April 2026 brings a range of important deadlines, responsibilities, and changes that small business owners, limited company directors, and sole traders need to be aware of.

Whether you’re managing your own business finances or working with an accountant, staying on top of key financial dates is essential to avoid penalties, remain compliant with HMRC, and plan effectively for the year ahead.

In this guide, we’ll break down the most important financial deadlines for the 2026/27 tax year, along with the key tax changes, including the introduction of Making Tax Digital for Income Tax (MTD ITSA).

Understanding the tax calendar can help you stay organised and avoid last-minute stress. Below are the key dates you need to keep in mind.

The new tax year officially begins on 6 April 2026. This is when updated tax rules come into effect, including the rollout of Making Tax Digital for Income Tax for eligible individuals.

It’s also the point at which you should begin tracking income and expenses for the 2026/27 tax year.

If you are self-employed or a sole trader, your second payment on account for the 2025/26 tax year is due by 31 July 2026.

Payments on account are advance payments towards your next tax bill, based on your previous year’s liability. Failing to make this payment on time can result in interest being charged by HMRC.

If you became self-employed or started earning untaxed income during the 2025/26 tax year, you must register for Self Assessment by 5 October 2026.

This applies to:

• New sole traders.
• CIS workers not previously registered.
• Individuals with additional untaxed income.

If you choose to submit a paper Self Assessment tax return, it must be filed by 31 October 2026.

However, most individuals now submit online, which gives you additional time.

This is one of the most important dates in the tax calendar.

By 31 January 2027, you must:

• Submit your online Self Assessment tax return for the 2025/26 tax year
• Pay any tax owed
• Make your first payment on account for the 2026/27 tax year

Missing this deadline can result in immediate penalties and interest charges.

Alongside the usual deadlines, the 2026/27 tax year introduces significant changes that will affect how individuals and businesses manage their tax obligations.

The most notable change is the introduction of Making Tax Digital for Income Tax for individuals earning over £50,000.

This affects:

• Sole traders.
• CIS workers.
• Landlords.

Instead of submitting one Self Assessment tax return each year, affected individuals will need to:

• Keep digital records of income and expenses.
• Submit quarterly updates to HMRC.
• Use HMRC-recognised software.
• Complete a final declaration at year-end.

This represents a major shift from annual to real-time tax reporting.

You can learn more about the requirements directly from HMRC here:
https://www.gov.uk/guidance/using-making-tax-digital-for-income-tax

For many sole traders and CIS workers, this will be the first time they are required to maintain fully digital accounting records.

The move to quarterly reporting means:

• More frequent deadlines
• Increased administrative responsibility
• Greater need for accurate, up-to-date bookkeeping

Without the right systems in place, this could lead to errors or missed submissions.

At CloudAccountant.co.uk, we offer tailored Making Tax Digital support to help you transition smoothly and stay compliant without increasing your workload.

While Making Tax Digital for Income Tax does not directly apply to limited companies yet, directors should still be aware of related changes and ongoing obligations.

Limited companies must continue to:

• File annual accounts with Companies House
• Submit Corporation Tax returns to HMRC
• Run PAYE payroll if taking a salary
• Keep accurate financial records

Future phases of MTD are expected to include Corporation Tax, so it’s important to start preparing early by adopting digital systems now.

Missing key financial deadlines can have serious consequences, including:

• Late filing penalties.
• Interest charges on unpaid tax.
• Increased scrutiny from HMRC.

For small business owners and contractors, this can quickly become costly and stressful.

Staying organised throughout the year allows you to:

• Plan for upcoming tax payments.
• Maintain accurate financial records.
• Avoid last-minute pressure.

Working with an accountant can also ensure nothing is overlooked.

At CloudAccountant.co.uk, we support small business owners, sole traders, CIS workers, and limited company directors with all aspects of their accounting and tax compliance.

Our services include:

• Self Assessment tax returns.
• Bookkeeping and cloud accounting.
• Payroll and limited company accounting.
• Making Tax Digital support.

We understand that every client is different, which is why we tailor our services to suit your needs and ensure you stay compliant throughout the year.

If you’re preparing for the 2026/27 tax year or want help navigating the upcoming changes, our team is here to support you.