Self Assessment for Freelancers: A Simple Guide

Do You Need to File a Self Assessment?

If you earn more than £1,000 from self-employment in a tax year (6 April to 5 April), you must register for self assessment and file a tax return. This applies whether you freelance full-time or alongside employment.

You must also file if you earn more than £100,000 overall, have income from savings or investments above certain thresholds, or are a company director. If in doubt, register — HMRC will confirm whether you need to file.

Step 1: Register with HMRC

Register for self assessment at gov.uk. You will need:

• Your National Insurance number
• Basic personal information
• The date you started self-employment

HMRC will send your Unique Taxpayer Reference (UTR) by post within 10 working days. Keep this number safe — you will need it every year.

Register by 5 October following the end of the tax year in which you started freelancing. Missing this deadline can result in a £100 penalty.

Step 2: Keep Records Throughout the Year

Good record-keeping makes the return straightforward and helps you claim every legitimate expense. Keep records of:

• All income received (invoices and bank statements)
• All business expenses with receipts or invoices
• Any other income (employment, savings interest, dividends)

HMRC requires you to keep records for at least five years after the submission deadline for that tax year.

Step 3: Understand Key Dates

• 5 April — end of the tax year
• 5 October — deadline to register for self assessment (for new filers)
• 31 October — deadline for paper tax returns
• 31 January — deadline for online tax returns and for paying the tax owed
• 31 July — second payment on account deadline

Most freelancers file online, which gives an extra three months beyond the paper deadline.

Step 4: Calculate Your Income and Profit

Your taxable profit is your total income from freelancing minus allowable expenses. Common allowable expenses include:

• Office costs (equipment, software, stationery)
• Travel to client sites
• Home office costs (a proportion of heating, electricity, broadband)
• Professional fees (accountant, solicitor)
• Training costs for existing skills
• Marketing and advertising

The key HMRC test is that expenses must be "wholly and exclusively" for business purposes.

Step 5: Calculate What You Owe

On your taxable profit, you pay:

• Income Tax at 20% (basic rate) above the Personal Allowance (currently £12,570), 40% between £50,270 and £125,140, and 45% above that
• Class 4 National Insurance at 6% on profits between £12,570 and £50,270, and 2% above that
• Class 2 National Insurance if your profits exceed the Small Profits Threshold (currently treated as a voluntary contribution for most people and calculated automatically in the self assessment)

Payments on Account

If your self assessment tax bill exceeds £1,000, HMRC requires you to make two advance payments toward the following year's tax bill:

• First payment on account: 31 January (same time as the current year's bill)
• Second payment on account: 31 July

Each payment is half your previous year's tax bill. This can be a significant cash flow shock in your first year — budget for it by setting aside roughly 25–30% of your income throughout the year.

Filing the Return

The HMRC online portal (Government Gateway) walks you through the return step by step. Most freelancers filing a simple self-employment return with no complex investments can complete it in under two hours if their records are in order.

Alternatively, an accountant can file on your behalf. Their fee is a deductible business expense and they will typically save you more in correctly claimed expenses than they charge.

Common Mistakes to Avoid

• Missing the 31 January deadline (automatic £100 penalty, increasing over time)
• Forgetting to include all income sources
• Underclaiming expenses through unfamiliarity with HMRC rules
• Not setting aside enough money to cover the bill

Start your return early — ideally in November — so you know what you owe before the January rush and have time to fix any errors.