What is Self-Assessment?
Self-Assessment is HMRC's system for collecting Income Tax from people whose tax is not automatically deducted through PAYE. If you are self-employed, a company director, a landlord, or you earn above £100,000, you almost certainly need to file a self-assessment tax return each year.
Who Needs to File a Self-Assessment Tax Return?
You must file a self-assessment tax return if, during the tax year, you:
- Were self-employed as a sole trader and earned more than £1,000
- Were a partner in a business partnership
- Were a company director
- Had rental income from a property
- Had income from savings, investments or dividends above the tax-free allowances
- Earned more than £100,000 in total income
- Received Child Benefit and you or your partner earned over £60,000
- Had income from abroad or lived abroad but had UK income
- Received a P800 notice from HMRC saying you did not pay enough tax
Self-Assessment Deadlines in Scotland
| Deadline | Date | What it covers |
|---|---|---|
| Register for Self-Assessment | 5 October (year 2) | First registration deadline |
| Paper return deadline | 31 October | For paper submissions only |
| Online return deadline | 31 January | Most common — online submission |
| Tax payment deadline | 31 January | Tax owed must be paid by this date |
⚠ Late Filing Penalties
Missing the 31 January deadline triggers an automatic £100 fine, even if you owe no tax. Penalties increase to £900 at 3 months, £1,200 at 6 months and further charges at 12 months.
Step-by-Step: How to File Your Self-Assessment
Register for Self-Assessment
If this is your first tax return, register at gov.uk using your National Insurance number. HMRC will post your Unique Taxpayer Reference (UTR) within 10 days.
Gather Your Records
Collect all income records (invoices, bank statements, P60/P45), expense receipts, any rental income statements, and dividend vouchers.
Calculate Your Income and Expenses
Total all income from every source and deduct all allowable business expenses. The difference is your taxable profit on which Income Tax and National Insurance are calculated.
Complete and Submit the Return
Log into your HMRC Government Gateway account and complete the online return, or use HMRC-compatible software. Submit before 31 January.
Pay Your Tax Bill
Pay any tax owed by 31 January. You can pay by bank transfer, debit card or Direct Debit through your HMRC account.
What Expenses Can You Claim on Self-Assessment?
Allowable expenses reduce your taxable profit and therefore your tax bill. Common allowable expenses include:
- Business mileage (45p per mile for first 10,000 miles)
- Office and stationery costs
- Equipment and tools
- Professional subscriptions and memberships
- Accountancy and professional fees
- Marketing and advertising
- Phone and broadband (business proportion)
- Training and CPD relevant to your work
- Home office costs if you work from home
What is Payment on Account?
If your tax bill is over £1,000, HMRC requires you to make advance payments towards next year's bill — called payments on account. These are 50% of your current bill, paid in January and July. Many people are caught off guard by this, so planning your cash flow is essential. We advise all self-assessment clients on their upcoming payment on account obligations.
📄 Let Us Handle Your Self-Assessment
We prepare and submit self-assessment tax returns for Glasgow sole traders, landlords, directors and freelancers. Fixed fee from £35/month. Free initial consultation.
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