How accounting works for builders is one of those questions that sounds simple until you’re in it. Construction has its own financial quirks, and most generic accounting advice doesn’t come close to covering them.

Why Builder Accounting Isn’t Like Running Any Other Business

Most businesses invoice when a job’s done. Builders often aren’t that simple. You might be halfway through a six-month contract, spending money on labour and materials every week, while the cash from the client comes in at agreed milestones or not until the end.

That gap between spending and getting paid is where a lot of building businesses quietly get into trouble. The numbers in your bank account can look reasonable while the underlying picture is under strain. Standard accounting software set up for a shop or a consultant won’t show you that clearly.

Job Costing: Knowing Which Jobs Actually Made You Money

Job costing is the practice of tracking costs and income for each individual project. Labour, materials, subcontractors, plant hire, anything that belongs to that job goes against it. At the end, you can see clearly what each job actually made, not just what you invoiced.

Without this, you’re running on gut feel. A builder I spoke to once thought his bigger contracts were his best earners. When we went through the numbers properly, one of his smaller domestic jobs was three times more profitable per week on site. He had no idea. That’s what job costing tells you, and it’s the kind of insight that shapes your quoting, your client choices, and your growth.

CIS and VAT: The Two Areas That Catch Builders Out Most Often

The Construction Industry Scheme (CIS) applies if you use subcontractors. As the contractor, you’re responsible for deducting tax from their payments and passing it to HMRC. Get it wrong and the liability stays with you, not the subcontractor. It’s a common source of unexpected tax bills for builders who didn’t realise the rules applied to them.

VAT adds another layer. The domestic reverse charge, which came in for most construction services in 2021, means VAT is handled differently between VAT-registered contractors and subcontractors. If you’re not set up for it correctly, you can end up accounting for VAT twice or missing it entirely. It’s worth checking your setup if you haven’t already, especially if your turnover is growing.

When DIY Accounting Stops Being Enough for a Building Business

If you’re handling your own books on a Friday evening and you can’t confidently say which jobs made money this quarter, that’s a sign the setup isn’t working for you. It’s not a failure. It’s just that the business has grown beyond what a spreadsheet or a basic accounts package can handle properly.

The right accountant for a builder understands CIS, knows the VAT rules for construction, can set up job costing in a way that actually makes sense for how you work, and will tell you where your margins are being eaten before it becomes a crisis. That’s what I do for builders across Scotland and the UK, and it’s a lot less complicated to sort out than most people expect when they first come to me.