Employed and self-employed at once — how the tax works

Updated: 14/07/2026 · 6 min read

Combining employment with self-employment is completely normal and administratively simple: your employer keeps operating PAYE on the salary, and the business goes on your Self Assessment — on the same return where you also report the job (from your P60). The calculation adds everything up and works out what extra is due.

How the tax adds up

You get ONE personal allowance, and the job usually consumes it. Business profit therefore starts being taxed from the first pound at your marginal rate — 20%, or 40% once total income crosses the higher-rate threshold. Put aside proportionally more from side income than a full-time sole trader would.

Step by step

Register for Self Assessment — employment changes nothing here
Track business expenses like any sole trader (they reduce the business profit)
After year end: P60 from the employer + your business income/expenses
Complete the employment AND self-employment sections of the return
The calculation adds income tax plus Class 4 NI on the profit

Watch out for

Tax code raids: HMRC sometimes tries collecting the business tax via your job’s tax code — you can opt out and pay through SA instead
Payments on account may start if less than 80% of your tax is collected at source
Your employment contract — check for exclusivity or competition clauses
Class 1 + Class 4 NI annual maximum — normally automatic, verify at high combined income

Two worlds, one set of records

Employment documents itself (payslips, P60). The business does not: every expense needs evidence. Keep business receipts and invoices flowing into one system from day one and the dual-income return becomes an evening’s work.

Every receipt captured, categorised and audit-ready.

Snap a photo or forward the email — Reclaim Day reads the vendor, amounts, VAT and date for you.

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Frequently asked questions

Do I have to tell my employer about my business?+

Not for tax purposes — HMRC does not inform them. Contractually, check your employment agreement for outside-work clauses.

How much tax will I pay on side income?+

Your marginal rate on the profit: typically 20%, or 40% on the part that pushes total income over the higher-rate threshold — plus Class 4 NI.

Do I get a second personal allowance for the business?+

No — one allowance per person, usually used by the salary. Business profit is effectively taxed from the first pound.

What if my side income is under £1,000?+

The trading allowance may exempt it from reporting — unless you already file a return, in which case you generally include it.

This guide is general information, not tax advice. Rules and figures change — check gov.uk (HMRC) for current rates, and speak to an accountant about your situation.