CIS monthly return deadline (19th of the month)

Under the Construction Industry Scheme (CIS), contractors must file a monthly return with HMRC by the 19th of the month following the end of the tax month — even when no payments have been made to subcontractors.

What is this filing?

The CIS monthly return (form CIS300) reports payments made to subcontractors and the tax deducted under CIS. Tax months run from the 6th of one month to the 5th of the next.

When is it due?

19th of the month following the tax month end. Nil returns must still be filed when no subcontractors were paid. Online filing is mandatory.

What's the penalty for missing it?

Late return: £100 (1 day late), additional £200 (2 months late), 5% of CIS tax or £300 (6 months late), same again at 12 months. Nil-return failures attract the same flat penalties.

How PenaltyProof helps

PenaltyProof's CIS monitoring (paid plans, opt-in) emails reminders for each monthly 19th deadline. Opt in once per practice; reminders fire for every applicable client.

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