Construction cash flow is the movement of money into and out of a construction business, from stage payments and retention releases to wages, materials, CIS and VAT. UK contractors often pay out months before they are paid, so even profitable firms can run short of cash.
Many construction businesses that fail are profitable on paper when they go under. The work was priced properly and the jobs were getting finished. What ran out was cash.
Construction cash flow is the gap between paying out for labour, plant and materials and actually being paid for the work. In this sector that gap is wider than almost anywhere else. This guide explains why, what causes it, and how to keep money moving through your business.
What Is Construction Cash Flow?
Construction cash flow is the movement of money into and out of a construction business over a set period. Money comes in through stage payments, valuations, retention releases and VAT refunds. It goes out on wages, subcontractors, materials, plant hire, CIS, VAT and Corporation Tax.
Construction Cash Flow vs Profit
Profit tells you whether a job made money. Cash flow tells you whether you can pay the bills while it does. A £200,000 job with a healthy margin can still leave you short for months if you are waiting 60 days for each valuation to be paid. Profit is an opinion about the past. Cash in the bank is a fact about today.
Positive vs Negative Cash Flow
Positive cash flow means more comes in than goes out. Negative means the reverse. A negative month or two at the start of a project is normal. The danger comes when several jobs hit that phase at once.
Why Construction Cash Flow Is Different for UK Contractors and Subcontractors
Most businesses sell something and get paid within weeks. Construction works the other way round. You deliver first and are paid later, in stages, after someone else has agreed the value of what you have done.
On top of that, UK contractors deal with features most other sectors never see:
- Retentions, where a slice of every payment is held back, often for a year or more after completion
- The Construction Industry Scheme (CIS), which takes tax off a subcontractor’s income before it reaches the bank
- The VAT domestic reverse charge, which means many subcontractors no longer hold the VAT on their sales until the return is due
- Long payment chains, where a delay at the top is passed down to every firm below it
The reverse charge deserves a mention of its own. Before March 2021, many subcontractors added 20% VAT to their invoices and paid it over to HMRC weeks or months later. That acted as a free short-term buffer. For work covered by the reverse charge, that buffer has gone, and some firms only noticed when their bank balance started to feel tighter. The reverse charge applies where a VAT registered subcontractor supplies another VAT registered, CIS registered contractor, but not to work for an end client. Each of these is manageable on its own. Together, they make cash flow the biggest financial risk for most construction firms
7 Common Construction Cash Flow Problems and What Causes Them
Late Payments From Clients and Main Contractors
Payment terms of 30 days often stretch to 60 or 90 in practice. Subcontractors at the bottom of the chain feel it most. Pay-when-paid clauses, where a main contractor only pays you once they have been paid, are generally banned under the Construction Act unless the client above them is insolvent, but delays still find their way down.
Slow Invoicing and Valuation Disputes
If applications for payment go in late or without supporting detail, the payment clock starts late too. One disputed variation can hold up a whole valuation.
High Upfront Costs for Labour, Plant and Materials
Wages go out weekly and materials are often paid on order. The income from the same job may not arrive for six to eight weeks.
Cost Overruns and Variations
Variations carried out on a verbal instruction are hard to get paid for. Overruns that are not spotted until the end of a job eat into cash you were counting on.
Paying Suppliers Before You Are Paid
Merchants and hire firms want paying on their terms, not yours. Each time you pay out first, you are funding the project from your own reserves.
Seasonal Fluctuations
Winter weather, the August slowdown and the Christmas shutdown all reduce how much work gets done and invoiced. Your overheads keep running regardless.
Poor Cash Flow Forecasting
Many firms watch the bank balance but never look ahead. Without a forecast, a shortfall in eight weeks’ time feels like a surprise when it was predictable all along.
How to Forecast Cash Flow: Milestone Payments and the S-Curve
A good construction cash flow forecast is built job by job, then rolled up to the whole business.
- List each live and secured project with its contract value and payment schedule.
- Map the expected costs month by month: labour, subcontractors, materials and plant.
- Map income by milestone or valuation date, then apply the payment terms to show when the cash actually lands.
- Deduct retentions and CIS where they apply.
- Add overheads, VAT, PAYE and Corporation Tax payments.
- Compare the forecast with what actually happened every month, and update it.
Plot a project’s cumulative costs over time and you usually get an S shape, known as the S-curve. Spending starts slowly, climbs steeply through the main build, then flattens towards completion. Income follows the same shape but lags behind. The gap between the two lines is the cash you need to fund the job, and it is widest mid-project.
Example (illustrative figures): Take a six-month, £300,000 fit-out. In the first two months you might spend £60,000 on labour and materials but receive only a small first valuation, paid 30 days after it is approved. By month three you could easily be £50,000 out of pocket before income starts to catch up. That figure, not the margin on the job, is the one to plan your funding around. Knowing where each job sits on its curve tells you when the pressure will come.
7 Ways to Get Paid Faster and Improve Cash Flow
- Submit invoices and applications for payment on the day they are due, with full supporting detail.
- Agree payment terms, valuation dates and retention release dates in writing before you start.
- Get every variation instructed and priced in writing before the work is done.
- Know your rights under the Construction Act. Your client must issue payment notices on time, and if a sum due goes unpaid you can suspend work on seven days’ notice.
- Ask for a mobilisation payment or deposit on larger jobs, especially where materials make up a big share of the cost.
- Chase retentions as soon as release dates arrive. They are easy to forget, and they are your money.
- Negotiate supplier terms that match your income cycle, not the other way round.
Invoice Finance vs Business Loans vs Overdrafts
Even with good habits, most growing contractors need some funding. The right type depends on the problem you are solving.
| Option | Best for | Watch out for |
| Invoice finance | Bridging the wait between invoicing and payment | Some providers will not lend against applications for payment or retentions, and fees add up |
| Business loan | Planned investment such as plant, vehicles or working capital for growth | Repayments are fixed, whatever happens to your income |
| Overdraft | Short dips in an otherwise healthy month | Can be cut or withdrawn at short notice, and is expensive if used permanently |
Invoice finance comes in two main forms. Factoring hands your sales ledger and credit control to the provider. Invoice discounting lets you keep collecting from customers yourself, which most established firms prefer. For plant and vehicles, asset finance such as hire purchase or leasing is often a better fit than a loan, because the asset itself secures the borrowing.
As a rule, short-term problems need short-term funding. Using an overdraft to cover a permanent shortfall only hides the real issue. Whatever you choose, arrange it while your accounts look healthy. Lenders are far more cautious once a cash shortfall has already hit.
Construction Cash Flow Checklist for UK Contractors and Subcontractors
- A rolling 13-week cash flow forecast, reviewed at least monthly
- A list of retentions held by each client, with release dates
- Applications for payment submitted on time, every time
- Every variation confirmed in writing
- Payment terms agreed before work starts
- Money set aside for VAT, PAYE and Corporation Tax
- Monthly management accounts showing profit and cash by job
- A funding facility agreed before you need it
How Julian Hobbs & Co Helps Construction Businesses Manage Cash Flow
Construction is one of our biggest sectors. We work with contractors and subcontractors across Hertfordshire, so we know how valuations, retentions and CIS play out in a real business, not just how they look in a textbook.
Our cash flow service gives construction clients monthly management accounts with a plain-English video walkthrough from Julian. We build forecasts around your actual jobs, flag tax bills before they land and spot problems while there is time to fix them.
If cash feels tighter than your profits say it should, book a call with Julian Hobbs & Co and we will help you get back in control.
FAQs: Frequently Asked Questions
Why do contractors have construction cash flow problems?
Mainly because they pay for labour, plant and materials before they are paid for the work. Long payment terms, retentions, CIS and valuation disputes all widen that gap.
How do you forecast construction cash flow on a project?
Map costs and income month by month using the payment schedule and realistic payment terms. Deduct retentions and CIS, then update it at least monthly.
What is the S-curve in construction cash flow?
It is the shape of a project’s cumulative costs over time: slow at the start, steep in the middle and flat at the end. Set against income, it shows when the job needs most funding.
How can subcontractors improve construction cash flow and get paid faster?
Submit applications on time with full backup, agree variations and payment terms in writing, and chase retentions promptly. Use your Construction Act rights when payment notices are missed.
What finance options help with construction cash flow?
Invoice finance bridges payment delays, loans suit planned investment and overdrafts cover short dips. Asset finance can also spread the cost of plant and vehicles.
What is retention in construction and how does it affect cash flow?
Retention is a slice of each payment, typically 3% to 5%, held back until the work is complete and defects are fixed. Half is usually released at practical completion and the rest after the defects period, often 12 months later. The Commercial Payments Bill would ban retentions in construction contracts. It has passed the House of Lords and is now with the House of Commons, so it is not yet law. As currently drafted, retention clauses in new contracts would become void two years after commencement, and existing ones after three years.
How does CIS affect a subcontractor’s cash flow?
Contractors deduct 20% from a registered subcontractor’s labour payments, or 30% if the subcontractor is not registered, and pay it to HMRC. A limited company can offset these deductions against its own PAYE bill, but a sole trader has to wait for their tax return. Gross payment status removes the deductions altogether if you meet HMRC’s tests, which include filing VAT returns and paying VAT on time. From April 2026, HMRC can also withdraw it with immediate effect in cases linked to tax fraud, and the wait to reapply after that kind of withdrawal is now five years.
What interest can I charge on late commercial payments?
Currently, under the Late Payment of Commercial Debts (Interest) Act 1998, you can charge interest at 8% above the Bank of England base rate, plus fixed compensation of £40, £70 or £100 depending on the size of the debt. This applies unless your contract already gives a substantial remedy for late payment. The Commercial Payments Bill would stop contracts removing this right and would cap payment terms at 60 days for larger businesses paying smaller suppliers, but these rules are not yet in force.
