Self-employed / sole trader

Self-Employment Tax: Register to Submit

Everything a sole trader needs, from your first invoice to your first tax return.

12 lessons About 77 minutes By Laura Michelle Davis ✓ Reviewed by TaxFly Admin Figures for 2026/27
A complete walkthrough of self-employment tax in the UK. You will learn when you have to register, which expenses actually count, how HMRC turns your income into a tax bill, and exactly what happens on the day you file. Every lesson ends with the real calculator so you can run the rule on your own figures.

By the end of this course you will be able to

  • Know whether you need to register as self-employed, and when
  • Work out your taxable profit from your income and expenses
  • Understand Class 2 and Class 4 National Insurance
  • Complete a Self Assessment return without guessing
  • Plan for payments on account so January is not a shock

What you will cover

Module 1

Getting started

Whether these rules apply to you at all, and what to do first.

Almost everything that goes wrong with self-employment tax goes wrong in the first year, and usually before any tax is even due. People register late, or register when they did not need to, or assume that because no money is owed yet, nothing needs doing.

This module deals with the three questions that come before any maths: does HMRC actually need to hear from you, what does the £1,000 trading allowance really do, and how do you get on the system without tripping a penalty on your way in.

  1. 1.1 Do you actually need to register? Your situation · 6 min · includes a calculator
  2. 1.2 The £1,000 trading allowance Lesson · 5 min · includes a calculator
  3. 1.3 Registering with HMRC and getting your UTR Lesson · 5 min
Module 2

Working out your profit

Turning what you earned into the number HMRC actually taxes.

HMRC does not tax your turnover, and it does not tax what you took out of the business. It taxes your profit: income minus allowable expenses. Every pound of legitimate expense you fail to claim is a pound you are taxed on unnecessarily.

This module is the one that saves people the most money, and it is where the most timid mistakes happen. New traders routinely claim nothing for the room they work in, nothing for the miles they drive, and nothing for the small costs that add up to hundreds over a year. The four lessons here fix that, and finish by assembling the profit figure that the rest of the course depends on.

  1. 2.1 Records you must keep Lesson · 5 min · includes a calculator
  2. 2.2 Which expenses you can actually claim Lesson · 8 min · includes a calculator
  3. 2.3 Working from home, and mileage Workshop · 7 min · includes a calculator
  4. 2.4 Turning income into taxable profit Workshop · 7 min · includes a calculator
Module 3

What you owe

Income tax, National Insurance, and filling in the return itself.

With a profit figure in hand, the bill follows mechanically. Two charges sit on top of the same profit: income tax, which behaves as it does for everyone, and National Insurance, which for the self-employed splits into two separate things with two separate purposes.

This module works through both, then walks the actual return, section by section. The form is long because it covers every kind of taxpayer. The part that applies to a sole trader usually is not.

  1. 3.1 Class 2 and Class 4 National Insurance Lesson · 7 min · includes a calculator
  2. 3.2 Filling in the return, section by section Workshop · 8 min · includes a calculator
Module 4

Paying, and staying out of trouble

The January shock, what late costs you, and what changes next.

Filing correctly is only half of it. The remaining risks are about timing and cash: the first January that costs more than you budgeted, the penalty regime that escalates faster than most people expect, and the shift to digital reporting that is changing how all of this works.

These three lessons are the ones that protect the money you saved in module 2.

  1. 4.1 Payments on account: the January shock Story · 7 min · includes a calculator
  2. 4.2 Deadlines, penalties and interest Lesson · 6 min · includes a calculator
  3. 4.3 What changes under Making Tax Digital Checkpoint · 6 min · includes a calculator

Finish with the exam

10 questions covering the whole course. Score 80% or more and you get a certificate of completion. You can retake it as many times as you like.

The exam needs a free account, so we can save your result. The lessons themselves never do.

Go to the exam

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Every figure follows HMRC 2026/27 rates and links to its gov.uk source.

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