What Is a Building Subcontractor Under the Construction Industry Scheme?

Under the Construction Industry Scheme (CIS), it is important for contractors to understand who counts as a building subcontractor and when CIS rules apply.

The definition does not depend solely on job titles. Instead, it is based on the type of work being carried out and how that work fits within HMRC’s construction rules.

Who Is a Subcontractor for CIS Tax Purposes?

A subcontractor is defined as any business or individual that agrees to perform construction operations for another business (a contractor or deemed contractor). This applies whether the work is done directly or through others such as employees or further subcontractors. Notably, a business typically considered a main contractor can be a subcontractor if hired by another contractor, such as a local authority.

Subcontractors can include:

• Companies, public bodies, partnerships and self-employed individuals.
• Labour agencies or staff bureaus that supply or employ workers for construction.
• Foreign businesses performing construction in the UK or its territorial waters.
• Local authorities or public bodies engaged in construction work for others.
• Gang-leaders who agrees with a contractor on the work to be done, and in turn receives payment for the work of the team.

Some businesses function as both contractors and subcontractors, paying others while also being paid for their services. These businesses must follow both sets of CIS rules depending on their role in each transaction.

How HMRC Defines a Building Subcontractor

For CIS purposes, a building subcontractor is a person or business that carries out construction operations for a contractor.

This can include individuals, partnerships, or companies engaged to carry out construction work as part of a wider project.

What Counts as Construction Operations?

Construction operations under CIS include a wide range of activities, such as:

• Building, altering, repairing, or demolishing structures
• Installing systems such as heating, lighting, or power
• Site preparation, groundwork, and finishing work
• Repairs and maintenance that form part of construction work

Some activities are specifically excluded, so not all work carried out on a site will automatically fall within CIS.

Common Areas of Confusion

Whether someone is a building subcontractor does not depend on whether they are self-employed or operate through a company.

It also does not depend on whether they supply materials, labour only, or a mixture of both. The key factor is whether the work itself counts as construction operations under CIS.

Why the Definition Matters

Understanding whether someone is a building subcontractor determines whether CIS deductions should be applied and whether the contractor has reporting obligations to HMRC.

Getting this classification right helps ensure deductions are handled correctly and records are kept in line with CIS requirements.

HMRC Guidance on CIS Definitions

HMRC explains what counts as construction operations and who falls within the Construction Industry Scheme on
GOV.UK.

Do You Need to Apply CIS Deductions?

Whether CIS deductions should be applied will depend on the type of work being carried out and whether it falls within HMRC’s definition of construction operations. For contractors and businesses in Farringdon and nearby areas such as Smithfield and Hatton Garden, CIGMA Accounting can review the nature of the work and help determine whether CIS applies in practice, ensuring deductions are handled correctly.