Every pound counts in a plumbing or heating business. So if you’re not claiming every legitimate travel expense you’re entitled to, you’re leaving money on the table every single week.
But here’s the thing: HMRC’s rules on business travel expenses are one of the most misunderstood areas in the trades. Get it wrong, and you’re either over-claiming — which puts you at risk if HMRC comes knocking — or you’re under-claiming, which means you’re paying more tax than you should.
Let me explain what you actually need to know.
The Difference Between Business Travel and Ordinary Commuting
The starting point is one simple question: is this journey from your home to a permanent workplace?
If it is, HMRC treats it as ordinary commuting. Think of it like this: where you choose to live is a personal decision, so the journey from your front door to your regular place of work is a personal cost. It doesn’t qualify for tax relief, full stop.
For a plumbing business, your permanent workplace might be your yard where you collect the van, a merchant where you pick up materials every morning, or an office where you run the admin side of the business. If your team members drive there every day, that commute doesn’t qualify — even if they stop at a customer’s property on the way.
This catches a lot of heating engineers out. They assume that because they’re in the van going to a job, it’s all business travel. But if the first stop is always the same place — whether that’s a depot, a merchant, or a fixed base — that leg of the journey is commuting, not business travel.
When Does Working From Home Change Things?
Here’s where it gets more interesting for sole traders and small plumbing business owners who run things from home.
If working from home is a genuine requirement of your role — not just a preference — then your home can be treated as a workplace. This isn’t just about answering emails at the kitchen table. To qualify, you need to be carrying out significant duties from home, and those duties must require facilities that are only realistically available at home.
When that’s the case, journeys from home out to job sites may qualify for tax relief. For a self-employed plumber who genuinely runs the business administration side from home — quotes, invoicing, scheduling — this is worth understanding properly.
Temporary Workplaces: The Rule Most Heating Engineers Don’t Know
This is the area that affects the day-to-day running of most plumbing and heating businesses. If you or a team member is attending a site for a specific project or short-term purpose, that site is likely to be treated as a temporary workplace. Travel to a temporary workplace qualifies for tax relief.
Consider a typical example in the trade: your business wins a contract to install the heating system across a new housing development. The engineer drives out to that development most days for the duration of the project. That travel qualifies — because it’s a specific project, not a permanent place of work.
But here’s where the 24-month rule comes in. If your team member is attending that same development for more than 24 months and spending 40% or more of their working time there, HMRC reclassifies it as a permanent workplace. From that point on, travel from home to site becomes ordinary commuting. Tax relief goes.
This matters more than most people realise. Long-term commercial contracts — schools, hospitals, housing associations, care homes — can easily run beyond two years. If your team members are regularly based at one of those sites, you need to know when the clock runs out.
Splitting a Journey: The Depot-to-Site Problem
This is where a lot of plumbing business owners get caught out in practice.
Let’s say your engineer starts every day at your depot — loads the van, checks the job sheet, picks up any parts needed — and then drives on to a temporary site. How is that journey treated?
The answer: it gets divided. The first leg — home to depot — is ordinary commuting. The second leg — depot to site — is business travel and qualifies for tax relief.
The exception is if the stop at the depot is genuinely incidental. If the engineer pulls in for thirty seconds to grab a single fitting and carries out no real work there, HMRC may treat the whole journey as business travel. But if they’re loading up, checking in, and doing something substantive, that depot stop creates the split.
This has a real impact on mileage claims. If your team members are claiming for the full journey from home to site when they stop at a depot or merchant on the way, part of that claim may not hold up under scrutiny.
Covering a Geographical Patch
Some plumbing and heating businesses operate across a defined area rather than from a fixed site. A business covering a city or a county, for example, where the engineers go wherever the jobs are each day.
In these cases, HMRC may treat the whole geographical area as the workplace. Travel within that area may qualify for tax relief. But the journey from home to the boundary of your patch is still treated as ordinary commuting. This is relevant if you’re a business that covers a wide area and your team members are driving significant distances before they reach their first job.
Subcontractors and Self-Employed Engineers
If you use subcontractors or self-employed engineers rather than employing team members directly, the same principles apply. Each contract they take on may be treated as a separate engagement, and travel from their home to the site is generally still ordinary commuting rather than business travel.
Where it does qualify is travel between different sites during the working day — moving from one job to the next. That’s business travel, regardless of employment status.
Multiple Fixed Bases
If your business operates from more than one fixed location — perhaps a depot on one side of town and an office or second yard on the other — travel between those locations qualifies for tax relief. But travel from home to either location is still ordinary commuting.
This is worth thinking about if you’ve grown your business to a point where you have more than one site, or if you regularly commute to a merchant or supplier as part of your working day.
Why Your Records Matter
Here’s the practical takeaway. HMRC’s travel expense rules are detailed, and what qualifies depends on the specific facts of each journey. If HMRC ever conducts a PAYE audit or compliance review of your business — and they do target the trades — your records are what stand between you and a tax bill.
What does good record-keeping look like for a plumbing or heating business?
- A mileage log for each journey: date, start point, destination, purpose, distance
- Evidence that a site was a temporary workplace and what project it related to
- Notes on any journeys that split between depot and site
- A clear record of when any site has been attended for close to 24 months
It doesn’t need to be complicated. A simple mileage app or spreadsheet updated daily will do the job. The businesses that get into trouble with HMRC aren’t usually doing something intentionally wrong. They’re the ones who assumed it would all be fine — and had nothing to show when someone came to check.
Running a profitable plumbing or heating business means knowing your numbers properly — from what you’re charging on each job to what you’re legitimately claiming. Once you’re ready to learn how to actually implement this in your business, the full step-by-step process is covered in my books.
Get The Quote Handbook here: https://amzn.to/3WzrTkJ
Get The Systems Handbook here: https://amzn.to/45aMvUH (also available in hardcover: https://amzn.to/4pA1WiF)
The more clearly you understand how money moves in and out of your business, the better placed you are to keep more of it.