How do I file a Self Assessment tax return for the first time as an electrician?

Add up every 2025-26 job, contractor and homeowner, before CIS was taken off. Put that total in turnover, the CIS deducted in its own box, then file online and pay by 31 January 2027.

Many electricians mix work for builders and electrical contractors with homeowner jobs. It covers 2025-26 returns, checked against GOV.UK on 18 October 2026.

Your jobs and where they land on the return

GOV.UK lists installing lighting and power systems as construction work under the Construction Industry Scheme (CIS). HMRC's CIS 340 guide says private householders are not contractors. Our guide on whether CIS applies to electricians covers the edge cases.

On the return, every job goes into one turnover figure: box 9 on the short pages, box 15 on the full pages. HMRC's notes say to include contractor pay at the full amount, before CIS deductions. Then total every deduction from 6 April 2025 to 5 April 2026 from your contractors' statements and put it in the CIS box. A contractor who takes a deduction must give you a statement within 14 days of the end of that tax month.

Short pages or full pages

GOV.UK says to use the short self-employment pages (SA103S) if your turnover was below the VAT threshold of £90,000, or would have been for a full year, and your affairs are fairly simple. Otherwise you use the full pages (SA103F). Both carry the CIS box: box 38 on the short pages, box 81 on the full pages.

Box 18 on the full pages is for paying others for construction work, not your deductions.

If you are VAT registered

HMRC's notes for the full pages say that on the cash basis your income and expenses would typically include VAT. If you include it, the net VAT you paid HMRC goes in as an expense, and any net VAT repayment goes in as income. Under traditional accounting your figures would typically exclude VAT.

For standard or reduced rated CIS work for a VAT-registered contractor, the domestic reverse charge applies unless the contractor tells you in writing it is an end user or intermediary supplier: your invoice states the VAT but leaves it out of the amount charged, and the contractor accounts for it. Homeowners are private customers, so their jobs carry normal VAT. See our reverse charge guide.

Costs, accounting and National Insurance

Cash basis is now the standard for sole traders, and under it tools and test equipment you buy to keep are expenses. GOV.UK also allows trade body membership related to your business and protective clothing like safety boots, and your scheme fee is a business cost. For the van, claim the business share of fuel, insurance, repairs and servicing, or a flat rate of 45p a mile for the first 10,000 business miles in 2025-26 and 25p after that. You cannot use the flat rate on a vehicle already claimed through capital allowances or as an expense. The electrician expenses guide has the full list.

For 2025-26, Class 4 National Insurance is 6% on profits between £12,570 and £50,270, and 2% above. Class 2 is treated as paid if your profit is £6,845 or more.

Over-deducted CIS is claimed back through your tax return. The sooner after 5 April you file, the sooner HMRC can repay you.

Deadlines, payments on account and penalties

• 5 October 2026: the date to tell HMRC you need a return. If you missed it, register now. HMRC sends a letter or email with a filing deadline 3 months from its date, but the tax is still due by 31 January 2027.
• 31 October 2026: paper returns.
• 30 December 2026: online, to have a bill under £3,000 collected through your PAYE tax code.
• 31 January 2027: online return and payment.

Payments on account apply unless you owed less than £1,000, or more than 80% of the tax was paid outside Self Assessment. Each is half of the tax you owed, due by 31 January and 31 July.

A late return costs £100 straight away, then £10 a day after 3 months, up to £900. At 6 and 12 months it is 5% of the tax due or £300, whichever is greater. Late payment adds 5% at 30 days, 6 months and 12 months, plus interest. With a reasonable excuse, you can appeal.

What this means for you

This return also decides when Making Tax Digital for Income Tax (MTD) starts for you. Qualifying income is your self-employment and property income added together, before expenses. PAYE wages do not count. For CIS work, in our reading the figure before deductions counts, as that is the turnover on your return. If the total for 2025-26 is over £30,000, MTD starts on 6 April 2027. Over £20,000 in 2026-27 means 6 April 2028.

If you started part-way through 2025-26, HMRC scales your income up to a full year if it has the information. An electrician who started on 6 October 2025 and turned over £18,000 by 5 April 2026 would be treated as having about £36,000, so MTD would start in April 2027.

Steps to file your first return as an electrician

1. Check you have your Unique Taxpayer Reference (UTR) and your HMRC online sign-in.
2. Collect every monthly CIS statement for 6 April 2025 to 5 April 2026, and ask contractors for any that are missing.
3. Total your homeowner and other non-CIS income from invoices and bank statements, including cash jobs.
4. Add both together for your turnover, and total your costs.
5. Choose the short or full pages, and put your total CIS deductions in box 38 or box 81.
6. Check your bill and whether payments on account apply, then submit and pay by 31 January 2027.
7. Run the free MTD check to see if MTD starts for you in April 2027.

The trades section has more guides for electricians. Our tax plans start once our HMRC registrations are complete. Until then you can join the waitlist, and no payment is taken.