If you’re self-employed in the UK, completing an annual self assessment tax return is unavoidable. But with the right preparation, it needn’t be a nightmare. Here’s everything you need to know — from registration to filing.
Who Needs to File Self Assessment?
You must file if you’re self-employed with income over £1,000, a company director, earning over £100,000, or receiving untaxed income (savings, investments). If you’re unsure whether you need to file, HMRC’s online checker can help.
💡 Key takeaway
The self assessment deadline is 31 January — miss it and you receive an automatic £100 penalty, even if you owe nothing.
How to Register for Self Assessment
Register online through HMRC’s website before 5 October in your second year of self-employment. HMRC will send your Unique Taxpayer Reference (UTR) by post — keep this safe. Late registration can result in penalties.
What Information You’ll Need
Income from self-employment, employment income and P60s, rental income, bank interest, pension income, capital gains, expenses records, and any student loan repayments. Having your bookkeeping in order throughout the year makes this straightforward.
Filing Deadlines and Penalties
The online filing deadline is 31 January. Paper returns must be filed by 31 October. Missing the 31 January deadline incurs an automatic £100 penalty, increasing significantly if further months pass. Tax payment is also due by 31 January.
Payments on Account
If your tax bill exceeds £1,000, HMRC requires you to make “payments on account” — two advance payments of 50% of the previous year’s tax, due 31 January and 31 July. This catches many self-employed people off guard in their second year of trading.
Frequently Asked Questions
Can my bookkeeper file my self assessment?
Yes — a qualified bookkeeper can prepare and file your self assessment on your behalf, ensuring all allowable expenses are claimed and the return is accurate.
What happens if I file late?
An automatic £100 penalty for up to 3 months late, then £10 per day up to 90 days, then further penalties at 6 and 12 months. Always file on time, even if you can’t pay.
What if I can’t afford my tax bill?
Contact HMRC before the deadline to arrange a Time to Pay arrangement. They will often agree to a payment plan. Do not ignore the bill.
