Self-Employment Tax 2026: National Insurance, Allowable Expenses & Tax Deadlines

Understanding Self-Employment Tax in the UK

As a self-employed person, you're responsible for calculating and paying your own Income Tax and National Insurance contributions. Unlike employees, where taxes are deducted automatically, sole traders and freelancers must:

• Track all business income and expenses throughout the year
• Calculate their taxable profit
• File tax returns by strict HMRC deadlines
• Pay Income Tax and National Insurance contributions
• Keep detailed records for six years

From April 2026, Making Tax Digital for Income Tax (MTD ITSA) introduces a major change: instead of one annual Self Assessment return, qualifying sole traders must submit quarterly updates to HMRC plus a Final Declaration. Understanding how self-employment tax works—and the new 2026 requirements—is essential to avoid penalties and keep more of your income.

National Insurance for Self-Employed: How Much Will You Pay?

National Insurance contributions for the self-employed come in two types: Class 2 and Class 4. Both are calculated based on your business profit, and both contribute to your State Pension eligibility.

Class 2 National Insurance (Fixed Amount)

Class 2 NI is a fixed weekly contribution regardless of how much profit you make. For 2025-26, the rate is £163.80 per year (approximately £3.15 per week).

Class 4 National Insurance (Percentage-Based)

Class 4 NI is calculated as a percentage of your annual taxable profit, similar to Income Tax. For 2025-26:

• On profit between £11,908 and £50,270: 9% contribution
• On profit above £50,270: 2% contribution

Worked Example: National Insurance Calculation

Claiming Allowable Business Expenses

One of the most important ways self-employed people reduce their tax bill is by claiming allowable business expenses. The more expenses you legitimately claim, the lower your taxable profit—and the less Income Tax and National Insurance you pay.

However, HMRC has strict rules about what qualifies as an allowable expense. You can only claim costs that are wholly and exclusively for your business.

Common Allowable Expenses

Home Office Expenses: The Simplified Method

If you work from home, you can claim a deduction for your home office. HMRC offers a simplified method:

• £26 per month (£312/year) for one room used exclusively as an office
• No need to calculate exact utility bills or mortgage interest
• Simply claim the flat rate—HMRC won't question it

How to Calculate Your Taxable Profit

Your taxable profit is the foundation of your Income Tax and National Insurance calculations. It's straightforward:

This £42,000 taxable profit is then subject to:

1. Income Tax at your marginal rate (20% for most people)
2. Class 4 National Insurance at 9% (on profits between £11,908–£50,270)

MTD Income Tax: What Changes in April 2026?

Making Tax Digital for Income Tax (MTD ITSA) is transforming how sole traders and landlords file tax returns. Starting April 2026, the rules change significantly.

New Requirements from April 2026 (Phase 1)

If your qualifying gross income exceeds £50,000, you must:

• Keep digital records of all income and expenses throughout the year
• Submit quarterly updates (4 times per year) summarising income and expenses
• Submit a Final Declaration confirming your complete tax position by 31 January
• Use HMRC-recognised MTD software to make submissions

Quarterly Update Deadlines 2026-27

How MTD Changes Your Workflow

Instead of the old approach (keep records all year, file once annually by 31 January), MTD requires:

1. Quarterly record-keeping: Maintain digital records of income/expenses each quarter
2. Quarterly submissions: File updates to HMRC four times per year
3. Year-end final declaration: Confirm total income, claim reliefs, calculate final tax

This distributed approach reduces the January deadline rush and helps catch mistakes earlier in the tax year.

Important Deadlines for Sole Traders 2026

Tax Year Basics

The UK tax year runs from 6 April to 5 April the following year. So Tax Year 2025-26 runs from 6 April 2025 to 5 April 2026.

Key Deadlines for 2026

• 31 January 2026: File traditional Self Assessment (if not yet on MTD)
• 6 April 2026: Tax Year 2026-27 begins; MTD ITSA Phase 1 starts (if income >£50k)
• 7 August 2026: First quarterly MTD update due (Q1: April-July)
• 7 November 2026: Q2 quarterly update due (July-October)
• 7 February 2027: Q3 quarterly update due (October-January)
• 7 May 2027: Q4 quarterly update due (January-April)
• 31 January 2028: Final Declaration due (replaces traditional return)

Record-Keeping Requirements for Sole Traders

HMRC requires you to keep detailed business records to support every figure in your Self Assessment return. Here's what you must keep:

Records to Keep

• Income records: Sales invoices, receipts from customers, bank statements showing income deposits
• Expense records: Supplier invoices, receipts for purchases, utility bills, professional service invoices
• Bank statements: All business bank account statements showing income and expenses
• Payroll records: If you have employees, payroll documents and PAYE records
• VAT records: If VAT-registered, VAT invoices and VAT return documentation
• Asset records: Equipment purchases, depreciation calculations, disposal records
• Mileage log: If claiming vehicle mileage, detailed mileage records with business purpose

Retention Period: Six Years

You must keep all records for at least six years from the end of the tax year they relate to. For example, records from 2025-26 must be kept until 5 April 2032.

Records can be digital (photos of receipts, spreadsheets, accounting software) or paper. However, HMRC increasingly prefers digital records and specifically requires them under MTD rules.

Common Self-Employment Tax Mistakes to Avoid

Mistake 1: Not Claiming All Legitimate Expenses

Many self-employed people leave money on the table by not claiming all allowable expenses. Common forgotten deductions include home office costs, professional memberships, training courses, and vehicle mileage.

Solution: Work through the allowable expense categories systematically. If it's wholly and exclusively for your business, claim it.

Mistake 2: Mixing Personal and Business Finances

Using one bank account for personal and business transactions makes record-keeping chaotic. When HMRC asks for evidence, you'll struggle to produce clear documentation.

Solution: Open a separate business bank account. This instantly separates personal spending from business transactions, simplifying record-keeping.

Mistake 3: Poor Record-Keeping

Losing receipts, forgetting to record transactions, or maintaining messy files creates problems during HMRC audits. You may end up unable to substantiate your claims.

Solution: Implement a simple system: photograph receipts immediately, record them in a spreadsheet weekly, and store digital files in a cloud backup (Google Drive, Dropbox, OneDrive).

Mistake 4: Missing the January 31st Deadline (or Future Quarterly Deadlines)

Late tax returns trigger automatic HMRC penalties, regardless of your circumstances. From 2026, missing quarterly deadline also incurs penalties.

Solution: Mark all deadlines in your calendar 6 months in advance. Submit returns 7-10 days early to avoid last-minute technical issues.

Mistake 5: Not Planning for Your Tax Bill

Many self-employed people are shocked when their tax bill arrives. They didn't set aside money to pay it.

Solution: Estimate your annual tax bill and set aside money monthly. A simple rule of thumb: save 25-30% of your profit for Income Tax and National Insurance.

Frequently Asked Questions

Do I need to register as self-employed?

Yes. If you earn more than £1,000 from self-employment in a tax year, you must register as self-employed with HMRC within 3 months. Even if you earn less, registering is recommended to establish a Self Assessment record.

What happens if my profit is below the Personal Allowance?

If your profit is below your Personal Allowance (£12,570 for 2025-26), you pay no Income Tax. However, Class 2 National Insurance still applies if your profit exceeds around £6,725. You should still file a Self Assessment return to record your profit accurately.

Can I claim a loss against other income?

Yes. If your business makes a loss, you can offset this against other income, such as employment or rental income, to reduce your overall tax bill. Losses can also be carried forward to reduce future year profits. This is a powerful tax-saving tool for struggling businesses.

Do I need to register for VAT as self-employed?

You must register for VAT if your turnover exceeds £90,000 in any 12-month period. Below this threshold, VAT registration is voluntary. If VAT-registered, you must file VAT returns using MTD software.

What if I have expenses that straddle two tax years?

Claim expenses in the tax year the invoice is dated, or when payment is made for cash-basis taxpayers. If you invoice a client in March 2026 but receive payment in May 2026, the income counts in 2026-27 under the accruals basis. For expenses, claim them when incurred, not when paid.

When does MTD apply to partnerships?

MTD for Income Tax currently applies only to sole traders and landlords. Partnerships are expected to be brought into MTD scope at a later date, but HMRC has not confirmed a timeline yet. Stay tuned for updates.

Can I do my own tax return or must I use an accountant?

You can do your own Self Assessment return. However, many self-employed people use accountants for accuracy, peace of mind, and tax planning advice. With MTD from 2026, using HMRC-recognised software is mandatory, but you can do it yourself or have an accountant help.

Conclusion: Stay Compliant, Maximise Your Tax Efficiency

Self-employment offers flexibility and independence, but managing your own tax obligations requires discipline. Key takeaways:

• Know your tax deadlines: From 2026, quarterly MTD updates replace annual returns for businesses over the income threshold
• Claim all legitimate expenses: This directly reduces your tax bill and improves cash flow
• Keep meticulous records: Digital records required under MTD; keep them for six years minimum
• Calculate your National Insurance: Class 2 and Class 4 contributions can be substantial; plan for them in your pricing
• Use MTD-compliant software: From April 2026, you'll need official software to file quarterly updates—HMRC-recognised tools like 1 1 MTD Bridge make this straightforward

Starting your own business is exciting. Managing tax properly ensures you keep more profit, stay compliant with HMRC, and avoid penalties. Whether you're a freelancer, contractor, or running your own company, these principles apply. Get your record-keeping system in place now, and you'll be ready for MTD compliance in 2026 and beyond.