Most subcontractors spend all their energy winning work. They don't spend enough time choosing who they win it from.
A bad main contractor costs more than no work at all. Chasing payments for months. Variations refused. Final accounts slashed. Retention never released. These problems eat your profit and your time.
Here's how to evaluate a main contractor before you sign anything.
Step 1: Check Their Payment Track Record
Payment is the foundation. Nothing else matters if they don't pay.
What to check:
- Government payment practices data. Large companies have to report. From 6 April 2025 that means a company that exceeded two of three thresholds on its last two balance sheet dates: £54 million turnover, £27 million balance sheet total, 250 employees (GOV.UK guidance).
- The company's page on Construction Rating, which shows payment practices figures and other financial signals from public records. Here's how they work.
- Companies House accounts. Look at trade creditors relative to turnover.
- County Court Judgments. Several CCJs means several creditors who had to go to court to get paid.
If a contractor has a history of late payment, they won't change for your project. Move on.
Step 2: Read the Subcontract
Actually read it. All of it. Before you sign.
Red flags in contracts:
- Payment terms over 60 days
- Retention above 5%
- Defects liability periods over 12 months
- Unlimited set-off rights
- Onerous variation procedures designed to make claims difficult
- Any language that conditions your payment on the contractor being paid by their client
The Commercial Payments Bill would make 60 days the maximum payment term in most business contracts and ban cash retentions in construction after a transition period. On 14 October 2026 it was still before Parliament and not law, so for now your contract terms are what count.
If the contract is heavily weighted against you, negotiate. If they won't negotiate at all, that tells you something about how they view the relationship.
Step 3: Visit One of Their Current Sites
You can learn more in 30 minutes on a live site than in hours of desk research.
Things to observe:
- Is the site clean and well organised?
- Are welfare facilities decent? Clean toilets, drying room, canteen.
- Is the site board up to date?
- Do operatives look like they know what they're doing today?
- Talk to a subcontractor on site. Ask them how it's going.
If the contractor won't arrange a site visit, ask yourself why.
Step 4: Check Their Financial Health
A contractor that goes bust mid-project leaves you with unpaid invoices and little chance of recovering them. Our register of 229 UK construction failures shows the last accounts each failed firm filed and how its insolvency unfolded.
Check Companies House for:
- Filed accounts (late filing is a red flag)
- Net assets (negative means they owe more than they own)
- Cash at bank (low cash and high creditors is a danger sign)
- Director changes (frequent changes suggest instability)
Consider running a credit check through Creditsafe or Experian Business. Prices vary by provider, and a single report is a small cost next to tens of thousands at risk.
Step 5: Ask Around
The construction industry is small. Someone in your network has worked for most of the main contractors in your area.
Good questions to ask:
- Did they pay on time?
- How was the final account?
- Would you work for them again?
- How did they handle problems on site?
Step 6: Trust Your Instincts
If something feels wrong during the tender process, it usually is.
Pressure to start before the contract is signed. Vague answers about payment dates. A QS who won't return calls. These aren't just annoyances. They're predictions of how the project will go.
Good work will come. A bad contractor will cost you more than waiting for the right opportunity.
The Quick Checklist
Before signing any subcontract, make sure you can answer yes to all of these:
- Have you checked their payment record?
- Have you read the full subcontract?
- Are the payment terms reasonable (ideally 30 days, and no more than 60)?
- Is retention 5% or less with a 12-month defects period?
- Have you checked Companies House for financial health?
- Have you spoken to other subcontractors who've worked for them?
One hour of due diligence can save you months of problems. Make it a habit for every new contractor you work with.
Construction Rating lets subcontractors review the main contractors they work for. If you've worked for one, add your experience.