Register with HMRC for CIS before starting work as a subcontractor—delayed registration can result in 30% deductions instead of 20%.

Provide your Unique Taxpayer Reference (UTR) and National Insurance number to contractors for verification to ensure correct deduction rates.

Understand deduction rates: 20% for registered subcontractors or 30% if unregistered, directly impacting your cash flow and tax position.

Keep all CIS statements from contractors, detailing gross payment, deductions, and net payment, as proof for your tax return.

Report CIS income and deductions accurately on your Self Assessment tax return each year, including any overpaid tax to claim back.

Claim back overpaid deductions if your total tax liability is lower than the amounts deducted, which can be done through your tax return.

Maintain detailed records of all construction work, including invoices, payment dates, and contractor details, for at least six years.

Know that CIS applies to most construction activities like building, repairs, and demolition—check HMRC guidelines if unsure about specific work.

If working with multiple contractors, verify each has your correct CIS details to prevent errors in deductions and reporting.

Be aware of HMRC penalties for late registration, incorrect returns, or non-compliance, which can include fines and interest charges.