Most self-employed engineers pay more tax than they need to, because claiming everything you’re entitled to takes records nobody keeps at the time.

Here are five deductions UK heating and plumbing firms commonly miss.

1. Vehicle Expenses

Your van is your office, your workshop and your delivery vehicle, and HMRC gives you two ways to claim it.

Option A: Simplified Mileage Rate

45p per mile for the first 10,000 business miles, then 25p per mile after that.

Option B: Actual Costs

Claim the business percentage of fuel, insurance, road tax, MOT and servicing, repairs, and lease or finance payments.

Newer or more expensive vehicles usually do better on actual costs, older and cheaper ones on the mileage rate. Run the numbers both ways before you pick, because you’re largely stuck with the choice for that vehicle.

Whichever you choose, keep a mileage log. A spreadsheet with date, destination and miles is enough. Without records HMRC can deny the claim entirely.

2. Tools and Equipment

Everything you buy to do the job is deductible: hand tools, power tools, PPE and safety boots, and workwear that is branded or protective rather than clothes you’d wear anyway. Power tools come off in full in the year you buy them, under the Annual Investment Allowance.

The test is simple. If you wouldn’t buy it except for work, it’s probably deductible.

Keep receipts. A photo on your phone counts, as long as the date, amount and item description are readable.

3. Working from Home

You do admin at home even if you’re on site all day: quoting, invoicing, ordering materials, answering emails.

HMRC’s simplified rate pays £10 a month for 25 to 50 hours of home working, £18 a month for 51 to 100 hours, and £26 a month beyond that.

You can instead calculate the business proportion of electricity and gas, internet, council tax, and mortgage interest or rent. Use one room out of five primarily for business and you can claim 20% of household costs for the time it’s used.

4. Training and Professional Development

Training related to your current trade is deductible: Gas Safe renewal, 18th Edition, CSCS cards, professional body memberships, BS 7671 and building regulations guides, and online courses in business skills or software.

Training for a completely new trade is not. A heating engineer retraining as an electrician can’t claim it. A Gas Safe engineer adding an OFTEC oil qualification or getting up to speed on heat pumps can.

5. Phone and Technology

Your phone is a business tool, so claim the business percentage of the monthly bill. A separate work phone is 100% deductible. So are accounting apps, job management tools and cloud storage, and a computer or tablet in proportion to business use.

Bonus: Often Overlooked Deductions

Parking and tolls on business journeys, trade waste disposal fees, advertising including your website and van signage, public liability and professional indemnity and tool insurance, and accountancy fees. The cost of getting your tax done is itself tax-deductible.

How Much Could You Save?

A self-employed heating engineer earning £45,000 might have £8,000 to £12,000 of legitimate deductions they aren’t fully claiming. At the basic rate that’s £1,600 to £2,400 a year.

Action Steps

Start tracking expenses now, with an app or a simple spreadsheet.
Photograph every receipt on the spot, before it goes through the wash.
Review last year’s return. You may still be able to amend it.
Talk to an accountant who works with trades. They usually pay for themselves several times over.

Everything listed here is legal and expected by HMRC. The only mistake is not claiming it.