Construction accounting is not standard accounting, and using the wrong approach costs builders real money through missed CIS refunds, incorrect VAT treatment, and tax surprises that should never happen. This guide covers the key areas builders get wrong, what a proper accounting setup looks like, and what to do if your current situation is not working.

Why accounting for builders is a different discipline entirely

Construction businesses face financial risks that most accountants simply are not set up to handle. According to BCIS, construction firms accounted for 17% of all insolvencies in England and Wales in July 2026, with 3,841 registered construction businesses becoming insolvent in the 12 months to July 2026. That figure is 19% higher than pre-pandemic 2019, and construction recorded the highest insolvency count across all industry sectors.

A major reason for that failure rate is financial mismanagement that goes unnoticed until it is too late. Builders often carry work in progress for weeks before billing, pay subcontractors before receiving payment themselves, and operate under the Construction Industry Scheme, which introduces deduction rules, verification requirements, and monthly CIS return obligations that a general accountant may not handle correctly.

Where most builders go wrong with their accounts

The errors that cause the most damage are not big dramatic mistakes. They are quiet, cumulative problems that only surface when a bank asks for reports you cannot produce, or when HMRC sends a tax bill that should have been smaller.

Not claiming CIS deductions correctly

CIS deductions are not a cost to your business. They are a prepayment to HMRC that gets offset against your tax liability at the end of the year. Many builders, particularly those operating through limited companies, do not reclaim these correctly. For limited companies, CIS deductions are offset against PAYE and National Insurance contributions first, and any surplus is then offset against the corporation tax bill. If this process is not managed properly, you are effectively giving HMRC an interest-free loan.

Getting VAT wrong on construction work

VAT in construction is complicated by the Domestic Reverse Charge, which applies when you supply construction services to another VAT-registered business in the supply chain. Under reverse charge rules, you do not collect VAT from the contractor above you; they account for it themselves. If you are applying standard VAT where reverse charge applies, or vice versa, every invoice you raise may be incorrect. The VAT Flat Rate Scheme may also be worth reviewing, but builders with significant material costs need to check whether the standard scheme gives a better result before committing.

What a proper accounting setup looks like for a building business

There is no single right structure for every builder. A sole trader operating under CIS has very different requirements to a limited company running a small team of employees and subcontractors. The steps below apply to both but will look different in practice.

1. Step 1: Confirm your CIS status and registration. If you work as a subcontractor, confirm you are registered with HMRC under CIS so that deductions are taken at 20% rather than 30%. If you act as a contractor who pays subbies, you must verify each subcontractor with HMRC before making any payment and submit monthly CIS returns. The Low Incomes Tax Reform Group explains the CIS registration process in plain English.
2. Step 2: Set up bookkeeping that tracks costs by job, not just by category. A bank statement will tell you that you spent money on materials. It will not tell you whether those materials were used on a job that made a profit or one that lost money. Recording costs and income at job level is the only way to know which contracts are worth taking and which are draining your margins.
3. Step 3: Review your VAT position before each VAT return. If your annual turnover is below £150,000 excluding VAT, the VAT Flat Rate Scheme may reduce your administration, but only if the Domestic Reverse Charge does not apply to the majority of your work. Check the flat rate percentage for your trade sector, and apply the limited cost trader test every VAT period, as your spending on goods can change quarter to quarter.

Once these foundations are in place, you have visibility over your business finances rather than discovering problems after the fact. Month-end management accounts then become a useful tool rather than a chore, because the underlying data is already correct.

What it costs to get construction accounting right

The honest answer is that the cost of getting it wrong is nearly always higher than the cost of doing it properly. A missed CIS refund, an incorrectly applied VAT rate across 12 months of invoices, or a tax bill that could have been reduced with basic planning all have a tangible cash cost. At STZ Accounting, limited company packages covering bookkeeping, accounts, corporation tax, payroll and CIS start at a fixed fee of £215 per month for businesses turning over up to £100,000. There are no tie-in contracts and no surprise bills. Sole trader packages including bookkeeping, VAT returns and self-assessment start at £150 per month plus VAT.

How to get started today

If your current setup is not giving you clear numbers, or if you are unsure whether your CIS deductions are being claimed correctly, the first step is a straightforward conversation. There is no obligation and no sales pressure. You describe your situation, David explains what needs to change and what it would cost, and you decide from there.

• Check your CIS registration status with HMRC and confirm whether you are receiving deductions at 20% or 30%. If it is 30%, contact HMRC to register and ask your contractor to amend the rate going forward.
• Pull together three months of bank statements and a list of your current jobs. This is usually enough information for David to assess your current accounting position and identify any immediate risks or quick wins on a free introductory call.