Self Assessment for electricians

Register, file, pay

1. Register for Self Assessment if your gross trading income is over £1,000 in a tax year. Deadline to tell HMRC is 5 October after that year ends (5 October 2026 for 2025/26).
2. Keep income and expense records as you go. HMRC can ask for them for at least five years after the 31 January filing deadline.
3. File the online return by 31 January 2027 for 2025/26 (paper was 31 October 2026). Pay the balancing payment the same day.
4. If last year’s bill was over £1,000, Payment on Account is due 31 January and 31 July, each 50% of that bill.

Full deadline calendar and penalty ladder.

What goes on the self-employment pages (SA103)

Turnover is invoices to customers and contractors, including materials you billed. CIS deducted is not an expense box. It is tax already paid on the calculation. Scheme fees and calibration sit in other or professional costs. Motoring is mileage or actuals, consistently.

Deadlines and penalties

Miss the online deadline and the late-filing penalty is £100 immediately, even if you owe no tax. After three months it is £10 a day (capped at £900). At six and twelve months HMRC add 5% of the tax due or £300, whichever is greater. Late payment is a separate 5% at 30 days, six months and twelve months, plus interest.

Mistakes electricians make on the return

• Net-of-CIS turnover.
• Forgetting calibration and scheme fees because they left the personal card.
• No van log.
• Materials for the house in the merchant account lumped in with jobs.
• Assuming the main contractor’s accountant “does everyone on site”.

If you register for VAT (threshold £90,000 of taxable turnover), domestic work and CIS jobs can have different VAT treatments. That is a reason to get advice before you cross the line, not a reason to ignore the sole-trader return you already have to file.

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