Good news first: yes, the system is designed exactly for businesses like yours — but the netting doesn't happen on the monthly CIS return. That return is only for the deductions you made from your own subcontractors. The deductions you suffered go through your payroll scheme instead. Here's how the two sides work.
Side 1 — you as contractor
Each month you file your CIS return reporting what you paid your subcontractors and the deductions you made (20% for registered subcontractors, 30% for unregistered, 0% for those with gross payment status). You pay those deductions to HMRC — they're advance payments towards your subcontractors' tax, not yours.
Side 2 — you as subcontractor (the offset)
As a limited company, you set the deductions suffered against what you owe HMRC through your payroll: send your Full Payment Submission (FPS) as usual, and at the same time send an Employer Payment Summary (EPS) showing the total CIS deductions suffered for the year to date. HMRC then nets them against your PAYE, NIC and CIS liabilities, and you pay the balance by the usual date. If the suffered deductions exceed what you owe in a month, the surplus carries forward to the next month automatically — and you tell HMRC in the EPS that you have nothing to pay. If there's still a surplus at the end of the tax year, you claim it back as a refund. One warning: don't try to do this through your Corporation Tax return — HMRC specifically says you may get a penalty for that.
Records to keep
Keep the monthly payment and deduction statements every contractor gives you — they're your proof. Also keep a running record of the CIS deductions you've used to pay your PAYE bill (form CIS132 is designed for this). If HMRC queries your claim, they'll ask for this evidence first, and they'll amend your claim based on what they can verify if you can't produce it.
Practical tip: reconcile monthly — total deductions suffered year-to-date on the EPS should match your statements. Doing this each month avoids the exact problem you're worried about: overpaying and waiting months for a refund.
