Self Assessment Tax Return for 2026 [Complete Guide]

If you are self employed, a landlord, or earning income outside PAYE, the 2026 tax year brings important responsibilities. Understanding how the Self Assessment system works, what has changed, and how to prepare properly can save you time, money, and stress.

This complete guide explains everything about the Self Assessment tax return for 2026, the key deadlines, the process of filing, and the changes that Making Tax Digital (MTD) brings.

Key points

• Self Assessment is required for many types of income ✅
  If you earn income outside of PAYE, such as self employment earnings, rental income, dividends, or foreign income, you must report it to HMRC.
• Making Tax Digital changes the reporting process 💻
  From April 2026, eligible sole traders and landlords must keep digital records and submit quarterly updates. Self Assessment becomes part of a continuous digital reporting cycle rather than a single annual form.
• All taxable income and allowable expenses must be tracked accurately ✍️
  You need to declare self employment income, property income, dividends, interest, foreign income, and capital gains. Expenses must be wholly and exclusively for business purposes.
• Deadlines are strict, and planning ahead matters 📅
  Key dates include registration by 5 October 2026, paper returns by 31 October 2026, and online submission by 31 January 2027. Staying organised throughout the year prevents last-minute stress and penalties.

What is a Self Assessment tax return?

A Self Assessment tax return is how individuals report income that hasn’t already been taxed through PAYE to HMRC. Instead of your tax being deducted automatically from wages, you calculate and report your income and expenses, then pay any tax owed directly.

You must file a Self Assessment tax return if you:

• Are self employed as a sole trader and earn over £1,000
• Work in a partnership
• Receive rental income
• Earn untaxed income, such as dividends or foreign income
• Earn over £100,000
• Need to claim certain tax reliefs
• Have Capital Gains Tax to report
• Receive Child Benefit, and you (or your partner) earn over £50,000

If you’re unsure whether you need to file, you can find the eligibility criteria on the government site.

How Making Tax Digital changes Self Assessment

From April 2026, sole traders and landlords with a total gross income over £50,000 must follow Making Tax Digital for Income Tax rules. The threshold will reduce to £30,000 in April 2027, and to £20,000 in April 2028.

Instead of filing once a year only, you will:

• Keep digital records using compatible software
• Submit quarterly updates of income and expenses
• Submit an End of Period Statement to finalise business profits
• Submit a Final Declaration to confirm all income

Self Assessment remains the mechanism for reporting your income to HMRC, but it now forms part of a broader, continuous digital reporting cycle.

For many business owners, this shifts the focus to maintaining accurate, real-time records throughout the year.

Key deadlines for Self Assessment 2026

Missing a deadline can trigger automatic penalties and interest. For the 2025–2026 tax year, these are the dates that matter:

Planning ahead, setting reminders, and keeping your records up to date throughout the year can make these deadlines far less stressful.

What income must you declare?

Even with digital reporting becoming mandatory, you still need to understand exactly which types of income must be included in your Self Assessment to ensure your records and submissions are accurate.

When completing your Self Assessment tax return, you’re responsible for declaring all taxable income, not just the money you think of as your ‘main’ earnings.

Here are the types of income that must be reported:

1. Self employment income

If you are a sole trader, you must declare all income from goods or services you provide. This includes bank transfers, cash payments, platform earnings, and overseas clients. Your total turnover must be reported before deducting expenses.

2. Property income

Rental income from UK or overseas property has to be declared. This includes long-term lets, short-term holiday rentals, and income received through letting platforms. You report the gross rental income, then deduct allowable property expenses.

3. Dividends

If you receive dividends from shares outside an Individual Savings Account, they must be declared, even if the amount falls within the dividend allowance. The allowance reduces the tax due, but the income still needs to be reported.

4. Interest

Savings interest above your Personal Savings Allowance is taxable. Depending on your total income, some or all of your interest may be taxed. Even if your bank deducts nothing at source, you may still need to declare it.

5. Foreign income

If you are a UK resident for tax purposes, you usually report worldwide income. This can include overseas rental income, foreign dividends, employment income from abroad, or interest earned in foreign bank accounts.

6. Capital gains

If you sell property, shares, or business assets and make a profit, you may need to pay Capital Gains Tax, which is the tax charged on the gain you make when disposing of certain assets. For the 2025–26 tax year, you can make up to £3,000 of capital gains before any Capital Gains Tax is due. If your total gains exceed that amount, the excess must be reported and may be taxed.

In some cases, Capital Gains Tax must be reported and paid earlier than the usual Self Assessment deadline, particularly when selling UK residential property, where a separate 60-day reporting and payment deadline applies.

Allowable expenses in 2026

To be deductible, a cost must be wholly and exclusively for business purposes. If an expense has both personal and business use, you can only claim relief for the business proportion.

For example:

• If 70% of your mobile phone use is business-related, you can claim 70% of the bill
• Everyday clothing isn’t allowable, even if worn to work, but specialist protective clothing is

Personal costs can’t be claimed, even if they are helpful for your job.

Below are the most common categories sole traders claim:

• Office costs: You can claim everyday running costs, such as stationery, postage, printer ink, business phone bills, and the work-related portion of your internet. Software subscriptions used to run your business also fall into this category.
• Travel expenses: Business travel is allowable. This includes fuel, parking, train fares, flights, taxis, hotel stays, and mileage (if you use your own vehicle for work). Travel between home and a permanent place of work doesn’t count as an allowable expense.
• Business insurance: This category includes policies directly connected to your trade, such as professional indemnity insurance or public liability insurance.
• Professional fees: Accountancy fees, legal advice, and subscriptions to approved professional bodies relevant to your industry can be claimed.
• Marketing and advertising: This category includes website hosting, domain names, paid advertising, social media promotions, printed materials, branding, and other promotional costs.
• Equipment and tools: Items such as laptops, machinery, office furniture, or specialist tools used for business purposes can be deducted. Depending on the type and value, these may be claimed through capital allowances rather than as day-to-day expenses.
• Software and digital subscriptions: You can deduct cloud accounting platforms, project management tools, design software, payment processing fees, and other systems used to operate your business.

What if I work from home?

If you run your business from home, you can claim part of your household costs.

You have two options:

• Claim a proportion of actual household bills, such as electricity, heating, rent, and council tax, based on business usage.
• Use HMRC’s simplified flat-rate method.

The method you choose must be reasonable and reflect genuine business use.

How to apply for and submit your Self Assessment tax return

Once you understand what you need to report, the next step is registering, completing, and submitting your return correctly. Here is how the process works in practice:

Step 1: Register for Self Assessment

If you have never filed before, you must register with HMRC.

You need to register by 5 October 2026 if you became newly self employed or started receiving untaxed income during the 2025–2026 tax year.

When you register, HMRC will issue:

• A Unique Taxpayer Reference (UTR)
• An activation code for your online account

Registration can take time, especially if you’re waiting for activation codes by post, so it’s best to do this as soon as you can.

Step 2: Set up your online account

Most people submit their return online through the Government Gateway.

To file online, you need:

• Your Government Gateway user ID
• Your password
• Your UTR

Step 3: Gather your documents

Before starting the return, collect all relevant records for the tax year:

• Total self employment income
• Expense records
• Rental income and property expenses
• Dividend statements
• Bank interest certificates
• P60 or P45 if you had employment
• Details of capital gains
• Student loan statements, if applicable

Having everything ready makes the process significantly faster and reduces errors.

Step 4: Complete the tax return

When you log into your Self Assessment account, select the correct tax year, and begin completing the return.

The form is structured in sections. You will:

• Confirm your personal details
• Answer tailoring questions so the system shows only relevant sections
• Enter income figures
• Enter allowable expenses
• Review the automatic tax calculation

The system calculates your tax liability once all sections are completed. You should review all entries carefully before submission.

Common mistakes at this stage include:

• Entering turnover instead of profit
• Forgetting small income streams
• Claiming expenses twice
• Missing payments on account already made

Make sure to check every figure before submitting.

Step 5: Submit your return

Once you confirm that everything is correct, submit the return.

After submission, you’ll receive a confirmation message. Keep a copy of your submission and calculation for your records.

If you realise you’ve made an error after submitting, you can amend your return.

You normally have 12 months from the filing deadline to make corrections online. After that, you may need to contact HMRC directly.

Step 6: Pay your tax bill

Your tax must also be paid by 31 January after the relevant tax year.

You can pay via:

• Bank transfer
• Debit card
• Direct Debit
• Through your online banking

If you owe more than £1,000 and less than 80% of your tax was collected at source, you’ll likely need to make payments on account towards the following year.

If you can’t pay in full, you may be able to arrange a Time to Pay agreement with HMRC, but interest will still apply.

Keeping your records organised for MTD and Self Assessment in 2026

With Making Tax Digital coming into effect in April 2026, staying organised is no longer optional for many sole traders and landlords. Accurate, real-time records will be essential in order to submit quarterly updates and prepare your End of Period Statement and Final Declaration.

Here are some practical ways to keep your information organised:

• Maintain digital records continuously: Record all income and expenses as they occur rather than waiting until year-end.
• Use compatible accounting software: Ensure your records meet digital submission requirements with HMRC-approved software.
• Categorise income and expenses immediately: Keep categories clear from the start to reduce errors and save time when submitting updates.
• Track payments on account: Monitor what you’ve already paid to avoid duplication or underpayment.
• Keep supporting documents in one place: Store digital copies of invoices, receipts, and bank statements to speed up and improve end-of-period reconciliation.
• Set reminders for quarterly submissions – Treat each quarter as a mini filing period to prevent last-minute stress.

By organising your finances throughout the year, you reduce errors, make Self Assessment easier, and stay compliant with MTD’s continuous reporting requirements.

Make Self Assessment effortless with ANNA

While good organisation can help, manually tracking, categorising, and submitting records can still be time-consuming. That’s where ANNA comes in.

ANNA is built to take the administrative burden off your shoulders by handling all your business finances and tax obligations automatically.

With ANNA, everything happens seamlessly – no spreadsheets, no manual logging, and no complicated setup. ANNA works quietly in the background, keeping everything on track.

Here’s what ANNA does:

• Captures and categorises expenses automatically: Records every transaction instantly and claims all allowable expenses
• Provides real-time tax estimates: Shows exactly how much tax you owe at any moment, avoiding surprises
• Saves automatically with smart money pots: Sets aside a percentage of income for tax, keeping payments to HMRC covered
• Creates, sends, and chases invoices automatically: Generates invoices, delivers them, and matches payments effortlessly
• Manages finances with a built-in UK business account: Gives access to cards, transfers, and seamless money management
• Calculates and files VAT returns automatically: Prepares and submits VAT returns fully compliant with Making Tax Digital
• Completes Income Tax Self Assessment automatically – for FREE: Submits quarterly updates, End of Period Statements, and Final Declarations without manual work, letting you file your 2026 Self Assessment for free (if you’ve already paid for alternative filing software, get the difference refunded)
• Sends automated reminders for deadlines: Notifies you of all upcoming filings and payments

As MTD reshapes Self Assessment, ANNA ensures you’re compliant without any stress or extra work.

So, try ANNA today and simplify your Self Assessment in 2026.