Key Differences Between Contractors & Subcontractors

By

Josh Krissansen

Reviewed by 

Nicholas Dunbar

and Zoe Mullan

Last Updated Dec 30, 2025

By

Josh Krissansen

Reviewed By

Nicholas Dunbar

and Zoe Mullan

In UK commercial construction, main (or principal) contractors engage directly with project owners to deliver complete construction programmes, while subcontractors perform specific scopes of work under the main contractor's management.

Understanding where each role begins and ends helps reduce overlap, streamline communication and keep projects moving without unnecessary friction.

This article breaks down the core differences between the two roles – from contractual relationships and site responsibilities to how each contributes to project delivery.

Independent Contractors in Construction

A significant portion of the United Kingdom's construction workforce operates as independent contractors. These individuals or businesses work under contract to deliver specific work packages, managing their own operations and commercial obligations.

Independent contractors function as standalone entities. They:

• Assume commercial risk
• Hold their own insurance (public liability, employers' liability and, where appropriate, professional indemnity)
• Meet tax and National Insurance requirements without employer oversight

This classification carries important implications, because under HMRC guidance, an independent contractor controls how work takes place and supplies their own tools.

In the UK, "independent contractor" is an umbrella term encompassing both main contractors and subcontractors. While the legal status may be similar, their contractual relationships and on site responsibilities differ significantly.

Contractors vs Subcontractors: Core Differences

Main Contractor Responsibilities

Contracting Party

Main contractors enter into a direct contractual agreement with the project owner. Under this agreement, they assume legal responsibility for delivering the entire scope of work. They also act as the principal contractor under the CDM Regulations 2015, preparing the construction phase plan and coordinating health and safety on site.

Furthermore, they manage a network of subcontractors and suppliers through a series of subcontracts issued under the main contract.

Responsibility

Main contractors maintain compliance with all applicable safety, regulatory and environmental standards. They oversee project communication between key stakeholders, including consultants, clients and subcontractors. Their role also includes:

• Project administration
• Tracking progress
• Issue resolution
• Document management
• Maintaining the 'Golden Thread' of information to satisfy Gateway 3 (Handover) requirements under the Building Safety Act 2022

Scope of Work

While they may self-perform certain aspects of the build, main contractors primarily focus on project oversight.

Their remit covers the entire project life cycle from early planning and procurement through to construction delivery and final handover. This includes:

• Sequencing trades
• Supervising subcontractors
• Maintaining control over programme, cost and quality performance

Subcontractor Responsibilities

Contracting Party

Main contractors, not project owners, contract subcontractors. Their agreements outline terms, deliverables, timelines and compliance obligations that align with the requirements of the main contract. Their legal and operational obligations flow through the main contractor.

Responsibility

Subcontractors deliver their agreed scope of work safely, on time and to specification. They must comply with:

• Relevant British Standards (e.g., BS 7671 for electrical installations)
• Health & Safety Executive (HSE) regulations, including the Work at Height Regulations 2005
• Site-specific safety or environmental requirements

Additionally, subcontractors coordinate with other trades and provide regular progress updates to the main contractor.

Scope of Work

Subcontractors typically focus on a single trade or specialist service. Their role remains confined to particular stages or segments of the build, with sequencing and access usually controlled by the main contractor.

In more complex projects, subcontractors may engage sub-subcontractors to handle highly specialised work.

UK Tax & CIS Obligations

Under the Construction Industry Scheme (CIS), main contractors must deduct income tax at source when paying registered subcontractors. HMRC sets deduction rates at 20% for verified subcontractors and 30% for unregistered subcontractors.

Moreover, contractors and subcontractors should review their employment status under IR35, which determines whether HMRC treats them as employees for tax purposes. For full guidance, see the HMRC CIS guide.

Improving Communication with Subcontractors

In construction, miscommunication remains a leading cause of delays, rework and site conflict. Main contractors need to take full responsibility for how they share information with subcontractors, from onboarding through to handover.

Subcontractors should know exactly where to find updated documents, who to report to and how to escalate issues. Consistent processes minimise confusion.

Key actions for improving communication with subcontractors include:

• Setting a clear chain of command so subcontractors understand reporting lines and approval points
• Using a centralised system to manage drawings, RFIs, variations and other project documentation
• Providing written site instructions rather than relying on verbal briefings or informal chats
• Running pre-start meetings to confirm daily tasks, site access and trade sequencing
• Documenting changes as they happen, with clear guidance on what should be done differently

Why Understanding the Difference Matters

Risk Management

Main contractors bear overall responsibility for project delivery and assume the commercial risk associated with it. Subcontractors, on the other hand, are responsible for delivering their specific scope in line with safety and compliance requirements.

If teams fail to define responsibility properly, key obligations may slip through or land with the wrong party. This can result in insurance complications, disputes or non-compliance with regulatory standards. With the HSE reporting 51 construction fatalities in 2023/24, the need for robust site controls is undeniable.

Communication & Reporting

Main contractors issue instructions, maintain documentation and coordinate updates across all trades. Subcontractors need clarity on how and when to report progress, raise concerns or respond to changes.

Establishing these expectations upfront reduces confusion and helps avoid errors that impact timelines and quality.

Payments & Workflows

Main contractors typically invoice the client based on project milestones or a cost-plus arrangement, whilst subcontractors usually receive payment via monthly Applications for Payment and may face retention clauses.

Example: A main contractor invoicing £1 million will typically retain 5% on each subcontractor payment, releasing half at practical completion and the balance at the end of a 12-month Rectification Period (formerly Defects Liability Period).

If the main contractor intends to pay less than the amount applied for, it must issue a pay-less notice under the Housing Grants, Construction & Regeneration Act 1996.

Treating these workflows as interchangeable can disrupt cash flow, cause processing errors and increase the risk of payment disputes.

Technology Needs

Main contractors require systems that support programming, subcontractor performance tracking and client reporting. In contrast, subcontractors are more likely to need simple, task-focused tools for site instructions, documentation and daily updates.

While shared platforms help unify project delivery, each role benefits from tailored workflows that match their scope and responsibilities. Competitors such as Causeway and Viewpoint Field View offer site-management tools, but few handle CIS deductions end-to-end.

Clear Roles Drive Project Success

Clear boundaries between contractors and subcontractors create more predictable delivery and fewer on site issues. When teams properly define roles, projects benefit from transparent accountability and optimal resource allocation across all phases.

Key considerations include:

• Roles and responsibilities
• CIS and IR35 considerations
• CDM 2015 and Building Safety Act duties
• Payment flow and retention
• Insurance and HSE compliance

FAQs

Can you be a contractor and a subcontractor at the same time? 

Yes. A firm may act as a main contractor on one project while performing as a subcontractor on another. Under CIS, it must register as both and apply deductions only to incoming subcontractor payments.

What is an example of a contractor and a subcontractor? 

On a London office fit-out, the main contractor (e.g., Mace) hires an electrical subcontractor (e.g., NG Bailey) to install cabling and lighting.

Written by

Josh Krissansen

48 articles

Josh Krissansen is a freelance writer with two years of experience contributing to Procore's educational library. He specialises in transforming complex construction concepts into clear, actionable insights for professionals in the industry.

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Reviewed by

Nicholas Dunbar

Content Manager | Procore

62 articles

Nick Dunbar oversees the creation and management of UK and Ireland educational content at Procore. Previously, he worked as a sustainability writer at the Building Research Establishment and served as a sustainability consultant within the built environment sector. Nick holds degrees in industrial sustainability and environmental sciences and lives in Camden, London.

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Zoe Mullan

27 articles

Zoe Mullan is an experienced content writer and editor with a background in marketing and communications in the e-learning sector. Zoe holds an MA in English Literature and History from the University of Glasgow and a PGDip in Journalism from the University of Strathclyde and lives in Northern Ireland.

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