The main contractor CIS playbook: tax months, statements and avoiding HMRC fines

Most building firms are both sides of CIS: a subcontractor to someone bigger, and a contractor to their own subbies. The contractor side is where the fines live. HMRC works in tax months from the 6th of one month to the 5th of the next, decided by the date you actually paid, not the invoice date.

1. 1

   Verify before the first payment

   Check each new subbie with HMRC using their UTR and NI number. HMRC tells you their rate — 0%, 20% or 30% — and gives a verification number. Pay at the wrong rate and HMRC can ask you for the difference.

2. 2

   Deduct from labour only

   Materials, plant hire and VAT are paid in full. Only labour has the deduction taken off.

3. 3

   Give statements by the 19th

   Every subbie you paid in the tax month gets a payment & deduction statement by the 19th after it ends.

4. 4

   File the monthly return by the 19th

   The CIS300 return lists every subbie paid and what was deducted. Late by one day is an automatic £100 fine, rising at 2 and 6 months.

5. 5

   Pay HMRC by the 22nd

   Pay the total deductions electronically by the 22nd.

6. 6

   Paid nobody? File a nil return

   Unless HMRC knows you are inactive, a month with no payments still needs a nil return or the £100 fine applies.

Subcontractor & CIS Invoicing keeps this routine for you: a subbie list with their verification number and rate, payments that drop into the right tax month (log them on site from the /cis phone app), a live countdown to the 19th, one-tap Email all statements, and return figures ready to submit on HMRC's website.