Construction Industry Scheme Knowledge Base

What Is the Construction Industry Scheme?

How CIS works, why it exists, and who it applies to.

Contractors vs Subcontractors

The definitions, obligations, and key differences under CIS.

Construction Operations: What Is In Scope?

Which types of work fall inside and outside CIS.

Deemed Contractors

When non-construction businesses must operate CIS.

Registering as a CIS Contractor

How and when to register with HMRC as a CIS contractor.

Registering as a CIS Subcontractor

Why registering reduces your deduction rate from 30% to 20%.

Gross Payment Status

The turnover, compliance, and business tests for 0% deductions.

The CIS Verification Process

How contractors verify subcontractors with HMRC before payment.

CIS Deduction Rates (20%, 30%, 0%)

The three CIS deduction rates and when each applies.

Materials Deductions Under CIS

How materials costs reduce the amount subject to CIS deductions.

Calculating CIS Deductions

Step-by-step worked examples of CIS deduction calculations.

Paying CIS Deductions to HMRC

When and how to send CIS deductions to HMRC.

Monthly CIS Returns (CIS300)

What to include in your monthly CIS return and how to file it.

CIS Filing Deadlines

Monthly, quarterly, and annual deadlines for CIS compliance.

Correcting CIS Errors & Amendments

How to fix mistakes on previously submitted CIS returns.

CIS Nil Returns

When and how to submit a nil return if you had no subcontractor payments.

Reclaiming CIS Deductions

How to reclaim CIS deductions via Self Assessment or Corporation Tax.

CIS and Self Assessment

Reporting CIS income and deductions on your SA tax return.

CIS for Limited Company Subcontractors

How limited companies handle CIS deductions and Corporation Tax.

CIS Penalties for Late Filing & Payment

Fixed, daily, and tax-geared penalties for missed CIS deadlines.

HMRC CIS Compliance Checks

What happens during a CIS compliance check and how to prepare.

Common CIS Mistakes to Avoid

The most frequent CIS errors and how to prevent them.