Self Assessment Late Filing Penalties Explained
UK Self Assessment penalties explained. £100 at one day late, £900 at three months, then £300 twice more — £1,600 in total even on a zero tax bill.
Tax & HMRC
Fifty-odd guides sit under this heading. They answer four questions, in this order.
Do I have to file at all? Whether you need to send a return and what the £1,000 trading allowance actually covers settle it for most people. Side income from a platform has its own wrinkle: Vinted, eBay and Etsy now report sellers to HMRC, and the line between a hobby and a business is not about how you describe it.
How do I file it? Filing your first Self Assessment, step by step is the sequence, including the 5 October registration deadline that catches people four months before they think about tax. Your UTR arrives by post around fifteen days after you register, so the order matters. Which return you are filing and when it is due, and if you miss it, what the penalties actually come to.
What do I owe, and what can I take off? Income tax bands for 2026/27, National Insurance, and how much to set aside as you go. On the other side: allowable expenses, the ones that are not allowable, simplified flat rates and capital allowances. If the bill is over £1,000, payments on account add half again — and you can reduce them when the year is going to be worse.
What is changing? Making Tax Digital for Income Tax is the big one, with quarterly deadlines and a points-based penalty system that works nothing like the old one. And if you cannot pay, Time to Pay exists and works better before the deadline than after.
Every figure on these pages links to its HMRC source and carries the date it was checked. General information, not tax advice.
Self-Employed National Insurance Rates 2026/27
Self-employed National Insurance for 2026/27: earn £7,105 or more and Class 2 is free. Earn less and protecting your record costs £189.80 a year.
Payments on Account: Why Your First Tax Bill Is 150%
A Self Assessment bill over £1,000 means HMRC asks for it plus half again in advance — both on 31 January. How payments on account actually work.
Allowable Expenses for UK Freelancers: 2026/27 List
The mileage rate rose from 45p to 55p in April 2026 and most guides have not caught up. What sole traders can claim, and the mistakes that cost money.
How to File Self Assessment as a Freelancer, Step by Step
Your first Self Assessment in order: tell HMRC by 5 October, file and pay by 31 January, and budget for the payment on account nobody warns you about.
MTD for Income Tax: What Changes for Sole Traders
MTD for Income Tax started 6 April 2026 for sole traders over £50,000. What quarterly updates involve, who is caught and when, what does not change.