Do CIS subcontractors have to file monthly returns?

No. Contractors file monthly CIS returns, form CIS300, by the 19th. A subcontractor files a yearly tax return and, from 6 April 2027 or 2028 depending on income, Making Tax Digital quarterly updates.

Under the Construction Industry Scheme (CIS), the paperwork runs one way. The contractor files a return each month listing who it paid and what it deducted, and gives you a statement. You use those statements once a year. This guide follows GOV.UK's contractor and subcontractor guidance, HMRC's CIS 340 guide and GOV.UK's Making Tax Digital pages, all checked on 17 October 2026.

Who files what

HMRC's CIS glossary names the contractor's monthly return as form CIS300. GOV.UK says contractors file it through the HMRC CIS online service or commercial software, and must declare on it that the subcontractors listed are not employees. GOV.UK's guidance for subcontractors sets no monthly or quarterly CIS filing of their own.

Where "quarterly CIS returns" comes from

There is no quarterly CIS return. The phrase usually mixes up one of two things.

Quarterly payments by small contractors. CIS 340 says a contractor whose average monthly payments to HMRC, including any PAYE, are below £1,500 may pay quarterly, for quarters ending 5 July, 5 October, 5 January and 5 April. It adds that contractors paying quarterly must still send returns monthly.

Making Tax Digital quarterly updates. Making Tax Digital for Income Tax (MTD) applies to sole traders, including subcontractors. GOV.UK says quarterly updates are summaries of your income and expenses, "not tax returns". Each covers the tax year so far, from 6 April, and you send one even if you had no income in that period. For CIS, GOV.UK says HMRC adds your CIS subcontractor deductions to your MTD tax return after the year ends, for you to check before you submit.

What a subcontractor does file

GOV.UK says that at the end of the tax year a sole trader sends a Self Assessment tax return recording total pay before deductions as income and total deductions as "CIS deductions". HMRC then takes the deductions off the tax you owe, and any balance is due by 31 January. Online returns for 2025-26 are due by 31 January 2027.

MTD adds quarterly updates for some. GOV.UK says that if your qualifying income, meaning self-employment and property income before expenses, was over £30,000 for 2025-26, you must use MTD from 6 April 2027. Over £20,000 for 2026-27 means starting on 6 April 2028. For subcontractors, that test uses gross pay before CIS deductions.

Take a sole trader joiner whose 2025-26 statements show £34,000 of gross pay for labour, with £6,800 deducted at 20%, and no other income.

In none of those years does the joiner file a monthly CIS return, unless the joiner starts paying others. Our guide on whether MTD applies to CIS subcontractors covers the income test and the refund route in detail.

When a subcontractor becomes a contractor

The monthly return becomes yours the moment you pay someone else for construction work. CIS 340 says a business that pays others and is paid by others follows the contractor rules for one side and the subcontractor rules for the other. You register as a contractor before your first subcontractor and file every month, including a nil return or an inactivity request in months when you pay nobody. Our guides to registering as a CIS contractor and the monthly return deadline cover the routine and the penalties.

What this means for you

If you only ever get paid under CIS, your filing is yearly, plus quarterly updates once MTD starts for you. Your monthly job is not filing but checking: each statement should arrive by the 19th and show the right gross pay, materials and deduction. Before you join Making Tax Digital, over-deducted CIS is claimed back through your Self Assessment tax return. Once you are in Making Tax Digital, HMRC adds your CIS deductions to your tax return, and any refund is requested separately through HMRC online services. Either way, the sooner after 5 April the return is filed, the sooner HMRC can repay you.

Steps to stay on top of your filing

1. Check whether anyone you pay does construction work for you. If so, you are also a contractor and the monthly return applies.
2. Keep every payment and deduction statement, and check each one when it arrives.
3. Add up your 2025-26 gross pay before CIS. If it and any other self-employed or rental income came to more than £30,000, MTD starts on 6 April 2027. If not, check 2026-27 against £20,000 for a 6 April 2028 start.
4. File your Self Assessment return early after 5 April, using gross pay as income and total CIS deducted as CIS deductions.
5. Once in MTD, put the four quarterly update dates in your diary.

The free MTD check shows when Making Tax Digital starts for you, and the trades section has more on CIS.