The CIS300 is the monthly return every contractor registered under the Construction Industry Scheme has to submit to HMRC, declaring the subcontractors paid, what they were paid, and what was deducted. It's separate from the Payment and Deduction Statements you send subcontractors, though the figures on both should always agree, since they come from the same underlying payments. Miss the return, even with nothing to declare that month, and HMRC's penalties start immediately.
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Every subcontractor paid for construction work in the tax month, their UTR and verification status, the gross amount paid, materials excluded from the deduction, and the tax deducted. It also requires a declaration that none of the subcontractors listed are actually employees.
By the 19th of the month following the end of the tax month, which itself runs 6th to 5th. A return covering the 6 April to 5 May tax month is due by 19 May.
If you didn't pay any subcontractors in a tax month, you still need to tell HMRC, either by filing a nil return or by requesting a period of inactivity. Simply not filing looks the same as filing late.
The CIS300 total for a subcontractor should exactly match what's on the Payment and Deduction Statement you gave them for the same tax month. If they don't agree, one of the two was calculated wrong.
£100 for being one day late, rising to £200 after two months, then the higher of £300 or 5% of the CIS deductions after six months, and again after twelve months. Persistent lateness can trigger further penalties on top.
Either. You can file it yourself through HMRC's online service or compatible software, or your accountant can file it on your behalf. What matters is that the totals filed match the statements you've actually sent subcontractors.
Yes, you can correct a return with HMRC if you find an error, though it's worth checking why the error happened, since it usually means a subcontractor's statement was also wrong and may need reissuing.
No. We calculate the totals from the same payment data used to generate your statements, so the two always reconcile, but filing the return with HMRC is still down to you or your accountant.
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