Three weeks from now, the UK tax year closes. For most plumbing and heating business owners, that date — 5 April 2026 — passes without much thought. And that’s a problem. Because the weeks between now and the end of the tax year are some of the most financially significant of your entire business calendar. What you do — or don’t do — between now and then could have a direct impact on your tax bill, your profit picture, and your financial standing for the year ahead.
Let’s look at what you should actually be doing right now.
Do You Know What Your Profit Looks Like This Year?
Before anything else, you need to know your numbers. Not approximately. Not roughly. Actually.
How much have you invoiced since 6 April 2025? How much of that has been collected? What have your costs been — materials, fuel, insurance, tools, subscriptions, wages? What’s left?
If you can’t answer those questions with reasonable confidence right now, that’s the first thing to fix. Because everything else — tax planning, decisions about spending, decisions about what to put aside — depends on knowing where you actually stand.
This isn’t about being an accountant. It’s about being a business owner. And right now, with three weeks of the tax year to go, you still have time to do something useful with the information.
The Expenses You Might Be Forgetting
One of the most common and costly mistakes plumbing business owners make is under-claiming legitimate business expenses. Not because they’re trying to avoid anything — but because they simply don’t know what they’re entitled to claim, or they forget to record it.
Here are some expenses that are regularly overlooked:
Use of home as office — if you do any admin from home (emails, quoting, invoicing), HMRC allows a claim for this.
Tools and equipment — anything purchased for the business in this tax year is a legitimate expense. Have you recorded everything?
Training and professional development — any courses, books, or memberships that relate to your trade or running your business.
Vehicle costs — if you use your van exclusively for work, all running costs are claimable. If you use a personal vehicle for some business journeys, those miles matter.
Phone and broadband — if you use your phone for work (and you do), a proportion is claimable.
None of these require a receipt from five years ago. They require you to have a habit of recording things as they happen — and if that habit has slipped, now is the time to catch up.
Do You Have Your Tax Bill Set Aside?
This is the question that keeps a lot of plumbing business owners awake in January. But it shouldn’t be a January problem. It should have been managed throughout the year — and if it wasn’t, three weeks before the year end is your last real chance to understand the number before it lands.
If you’re self-employed or running a limited company, your tax obligation doesn’t disappear when the year closes. It gets crystallised. And if you’ve had a reasonably good year — which many plumbing businesses have in 2025/26 — that figure could be meaningful.
Speak to your accountant now if you haven’t. Get an estimate. Know what’s coming. Don’t let April catch you off guard with a bill you haven’t prepared for.
The Bookkeeping Catch-Up You Need to Do
Even if you’ve been generally organised, the end of the tax year is a good time for a proper review.
Check that all your invoices are in your bookkeeping system. Check that all your expenses are recorded and categorised correctly. Chase any outstanding invoices that are still unpaid — not just for cashflow, but because outstanding amounts affect your taxable income picture.
If you’ve been keeping records in a spreadsheet, a notebook, or in your head, this is the week to get them into a proper system. Even a basic one. Not because HMRC will knock on your door tomorrow — but because a business that knows its numbers in March is in a much stronger position than one that doesn’t.
Three Actions to Take Before 5 April
One: Pull your numbers together. Total income in. Total costs out. Know your approximate profit for the year.
Two: Review your expenses list. Make sure everything legitimate is recorded. Don’t leave money on the table.
Three: Talk to your accountant. Even a fifteen-minute call in the next two weeks will give you clarity on what’s coming and what you can do about it.
The plumbing businesses that build real wealth over time are not always the most technically skilled or the busiest. They’re the ones that treat their numbers seriously — consistently, not just in a panic at year end.
If you’re ready to build that discipline into your business — understanding your pricing, your margins, and your profit — The Quote Handbook is the place to start. Grab your copy
here: https://amzn.to/3WzrTkJ
Get on top of your numbers this week. The tax year waits for no one.