- Self assessment expenses reduce your taxable profit when costs are incurred wholly and exclusively for business use.
- You can claim allowable expenses such as travel, software, marketing, staff costs, and working from home expenses.
- Using simplified expenses can reduce admin, but calculating actual costs may increase your total tax relief.
Self assessment expenses reduce the amount of profit you pay tax on. If you are self-employed, a freelancer, or a sole trader, claiming allowable expenses correctly can significantly lower your HMRC tax bill each year.
To qualify, costs must be incurred wholly and exclusively for business purposes. This includes everyday running costs such as software, travel, marketing, staff payments, working from home expenses, and business travel expenses. You can either calculate actual costs or use HMRC’s simplified expenses scheme, depending on what works best for your business.
If you would prefer your return prepared and submitted accurately without handling the calculations yourself, you can use a dedicated Self Assessment tax return service.
Understanding what you can and cannot claim before filing ensures you reduce your tax legally, avoid HMRC enquiries, and stay compliant each tax year.
What Are Self Assessment Expenses?
Self assessment expenses are business costs you deduct from your turnover before calculating taxable profit.
HMRC allows you to claim allowable expenses that are incurred wholly and exclusively for business purposes. This means the cost must relate directly to running your business, not personal use.
For example, if your turnover is £60,000 and you claim £15,000 in allowable expenses, you only pay tax on £45,000.
If you are unsure whether you need to file at all, our guide on register for Self Assessment explains who must submit a return and when.
You cannot claim expenses if you choose to use the £1,000 trading allowance instead of itemising costs. You must choose one method or the other for that tax year.
What Allowable Expenses Can You Claim?
Most self-employed businesses claim expenses across predictable categories. Below is a structured breakdown aligned with HMRC rules.
Office and operational costs
You can claim everyday running costs, including:
- Stationery and postage
- Printer ink and small office supplies
- Software subscriptions
- Phone and internet bills
- Cloud accounting tools
If you use services to create invoices or manage records, those costs qualify as allowable. You can see practical examples in our guide on how to create an invoice.
Larger equipment may fall under capital allowances rather than day-to-day expenses.
Business travel expenses
You can claim travel that is required for business purposes.
This includes:
- Train, bus and taxi fares
- Flights for business trips
- Hotel accommodation
- Parking and tolls
- Meals during overnight business travel
You cannot claim commuting between your home and your regular place of work.
If your travel involves a company vehicle, rules differ slightly. Our guide to company car tax explains how vehicle taxation interacts with allowable travel claims.
Vehicle and mileage claims
If you use a car or van for business, you must choose one method:
Method | What You Claim | Admin Level |
Simplified expenses | Flat rate per business mile | Low |
Actual costs | Fuel, insurance, servicing, repairs | Higher |
Under simplified expenses, you claim HMRC’s approved mileage rates. You cannot switch between methods for the same vehicle once chosen.
For many sole traders, simplified expenses reduce admin, but high-usage vehicles may benefit from calculating actual costs.
Working from home expenses
If you operate from home, you can claim a proportion of:
- Electricity and gas
- Internet
- Water
- Council Tax
- Mortgage interest or rent
You must divide personal and business use fairly.
Alternatively, you can use HMRC’s simplified flat rates for homeworking. Our detailed breakdown on claim tax back working from home explains both methods and how to calculate them correctly.
Staff and subcontractor costs
If you employ staff or contractors, you can claim:
- Salaries and wages
- Employer National Insurance contributions
- Pension contributions
- Subcontractor payments
- Training related to your business
Employer obligations can affect your cost base. Our overview of the cost of employing someone in the UK explains what to budget for beyond wages.
Financial, legal and professional fees
You can claim business-related professional costs, including:
- Accountant fees
- Solicitor fees
- Bank charges
- Business loan interest
- Insurance premiums
Understanding how tax interacts with different income types can also help you optimise your position. See our guide on tax on dividends UK if you operate through multiple income streams.
Stock, materials and bad debts
You can claim:
- Stock for resale
- Raw materials
- Direct production costs
If you use accrual accounting and an invoice becomes irrecoverable, you may write it off as a bad debt.
If you are unsure which accounting basis applies to you, our guide to sole trader tax explains how profits are calculated.
Marketing, subscriptions and software
Marketing costs are fully allowable if they promote your business.
This includes:
- Website hosting
- Online advertising
- Social media ads
- Branding
- Trade body subscriptions
You cannot claim client entertainment.
Clothing and uniforms
You can claim:
- Protective clothing
- Safety equipment
- Branded uniforms
You cannot claim everyday clothing, even if you only wear it at work.
Waiting until the Self Assessment deadline often leads to missed allowable expenses and rushed calculations. By reviewing your expenses every quarter, you can identify gaps, apply simplified expenses correctly, and ensure mixed-use costs are apportioned accurately. Regular checks also reduce the risk of HMRC errors and make year-end filing significantly smoother.
What Expenses Can’t You Claim?
Certain costs are specifically disallowed.
You cannot claim:
- Client entertaining
- Fines or penalties
- Personal expenses
- Commuting costs
- Capital repayments on loans
If HMRC identifies incorrect claims, penalties may apply. Our guide to HMRC and Companies House fines explains how enforcement works.
Should You Use Simplified Expenses Or Actual Costs?
Choosing the right method depends on your situation.
Category | Simplified Expenses | Actual Costs |
Vehicles | Fixed mileage rate | Fuel, insurance, repairs |
Homeworking | Flat monthly rate | % of household bills |
Living at business premises | Flat deduction | Apportioned running costs |
Simplified expenses reduce admin and are easier to track.
Actual cost methods can generate higher deductions if your expenses are substantial.
Review your position annually before submitting your return.
How Do You Record And Claim Self Assessment Expenses?
Accurate record keeping is essential.
You must:
- Keep receipts and invoices
- Separate personal and business transactions
- Maintain digital records
- Submit your return by 31 January
If you are unsure about deadlines, our guide on how to file a Self Assessment tax return explains the full process step by step.
You must also track income alongside expenses to calculate profit correctly.
How Sleek Manages Your Self Assessment Expenses
Each tax year, expense categories must be recorded, calculated, and submitted accurately to HMRC.
Sleek manages bookkeeping, categorisation, expense tracking, and tax return submission end to end. This ensures allowable expenses are captured correctly, simplified expenses are applied where beneficial, and deadlines are met without penalties.
If you want structured, compliant handling of your expenses and filing, a dedicated Self Assessment tax return service ensures your return is prepared accurately and submitted on time.
Disclaimer: The preceding information is not legal advice. This content is aimed to provide general guidance. For more formal or legal advice, contact Sleek directly.
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FAQs on Self Assessment Expenses
What are allowable expenses?
Allowable expenses are business costs that are incurred wholly and exclusively for the purpose of running your business. These costs reduce your taxable profit before Income Tax is calculated. Common examples include software, travel, marketing, staff wages, and working from home expenses. Personal or mixed-use costs must be apportioned correctly to qualify.
Can I claim expenses without receipts?
You are required to keep records of all business expenses, including receipts, invoices, and bank statements. While you do not submit this evidence with your Self Assessment tax return, HMRC can request proof during an enquiry. Without supporting records, expenses may be disallowed and additional tax, interest, or penalties could apply.
Can I claim working from home expenses?
Yes, if you use part of your home for business purposes, you can claim working from home expenses. You may either calculate a fair proportion of household costs such as electricity and internet, or use HMRC’s simplified flat-rate method. The method you choose should reflect actual business usage and be applied consistently.
What if my expenses are higher than my income?
If your allowable expenses exceed your income, you may generate a trading loss. In many cases, this loss can be carried forward to offset against future profits, reducing future tax liabilities. Depending on your circumstances, losses may also be offset against other income, subject to HMRC rules and eligibility conditions.
Can limited company directors claim self assessment expenses?
Limited company directors usually claim business expenses through their company accounts rather than through Self Assessment. However, they may still need to report dividend income, benefits, or other personal income on their tax return. The structure of your business determines how and where expenses should be claimed.
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Do I need an accountant to claim expenses?
You are not required to use an accountant to claim self assessment expenses. However, professional support reduces the risk of errors, ensures expenses are categorised correctly, and helps maximise allowable deductions. If you are comparing options, our guide on how much accountants charge for Self Assessment explains typical UK fees and what is included.
Can I claim expenses from previous tax years?
You must normally claim self assessment expenses in the tax year they were incurred. However, if you have already filed your return, you can amend it within 12 months of the 31 January filing deadline. After this window closes, changes are much more restricted. Reviewing your expenses before submission reduces the risk of missed claims.
