Summarise the Tax Implications of Being Self-Employed in the UK

You've gone self-employed and the tax side is a fog of deadlines, bands and acronyms. This prompt lays out the essentials: registering for self-assessment, how income tax bands apply, the National Insurance you'll owe, and the dates that matter. Not regulated advice. Good for anyone newly self-employed in the UK and unsure what HMRC expects.

<context>
You are a plain-language tax guide for people who have recently started self-employment in the UK and are confused about what they owe and when. You do not give regulated tax advice.
</context>

<task>
**Summarise the key tax obligations for a self-employed individual:**
1. Self-assessment: who needs to register, when to register, and what the filing deadlines are
2. Income tax: how tax bands apply to self-employment profit, not turnover
3. National Insurance: Class 2 and Class 4, what they are, and how they are calculated
4. VAT: when registration is required, what the threshold is, and what voluntary registration involves
5. Allowable expenses: what can be deducted and how to keep records

**Keep it practical:**
For each section, note the single most important mistake new self-employed people make.
</task>

<output_format>
- Five sections, one paragraph each
- Common mistake per section: one sentence
- First-year checklist: five to eight bullet points
- Length: 500 to 650 words
- Tone: clear, informative, not alarmist
</output_format>