How to File Your Self Assessment Tax Return Without the Stress
How to File Your Self Assessment Tax Return Without the Stress
Missing your self assessment deadline can cost you hundreds in penalties. We walk you through exactly what HMRC requires and how to avoid the most common mistakes.
Every year, thousands of self-employed individuals and sole traders across Yorkshire miss the HMRC deadline for filing their self assessment tax return — and the penalties can be severe. Whether you are filing for the first time or have been doing it for years, this guide walks you through everything you need to know to get it right.
Who Needs to File a Self Assessment Tax Return?
You must file a self assessment tax return if any of the following apply to you:
You are self-employed as a sole trader and earned more than £1,000
You are a partner in a business partnership
You earned more than £100,000 in the tax year
You received income from renting out property
You have income from abroad or from savings and investments
You received Child Benefit and your income exceeded £50,000
💡 Good to Know
Even if HMRC has not sent you a notice to file, you are still responsible for registering for self assessment if you meet the criteria. Failing to do so can result in penalties even before you have submitted anything.
Key Deadlines You Must Not Miss
DeadlineWhat It CoversPenalty if Missed5 OctoberRegister for self assessmentUp to 100% of tax owed31 OctoberPaper return deadline£100 immediate fine31 JanuaryOnline return + tax payment£100 + 5% surcharge after 30 days31 JulySecond payment on accountInterest + surcharge
⚠️ Important Warning
If your return is more than 3 months late, HMRC charges an additional £10 per day up to a maximum of £900. After 6 months, a further 5% of the tax due (or £300, whichever is greater) is added. Do not delay.
What Expenses Can You Claim?
One of the biggest advantages of self assessment is the ability to deduct legitimate business expenses from your taxable income. Many sole traders in Yorkshire leave money on the table by not claiming everything they are entitled to.
Allowable Business Expenses Include:
Office costs — stationery, phone bills, broadband
Travel costs — fuel, parking, train fares (not commuting)
Staff costs — salaries, subcontractor fees, pension contributions
Stock and materials used to make your product or deliver your service
Financial costs — bank charges, insurance, accountancy fees
Marketing — website costs, advertising, business cards
Training — courses directly related to your current business
✅ SAS Tip
If you work from home, you may be able to claim a portion of your household bills such as heating, electricity, and broadband as a business expense. HMRC has a simplified flat rate option of £26 per month if you work from home for 101+ hours per month.
Step-by-Step: How to File Online
Register for self assessment on the HMRC website and request your Unique Taxpayer Reference (UTR) — allow up to 10 working days for this to arrive by post
Set up your Government Gateway account using your UTR and the activation code HMRC sends you
Gather all your income records — invoices, bank statements, receipts for expenses
Log in to your HMRC online account and select Complete Your Tax Return
Fill in each section: employment income, self-employment income, other income, and expenses
Review your tax calculation — HMRC will show you how much you owe before you submit
Submit and pay before 31 January to avoid penalties
Common Mistakes to Avoid
Forgetting to include all sources of income, including bank interest and dividends
Not keeping receipts and records throughout the year — HMRC can ask to see them for up to 5 years
Entering figures in the wrong boxes, particularly for Class 2 and Class 4 National Insurance
Forgetting about payments on account — HMRC expects you to prepay next year's tax bill
Missing the registration deadline for new self-employed individuals
