A deemed contractor is a business whose main trade is not construction but which spends enough on construction work that HMRC treats it as a contractor for CIS purposes and requires it to operate the scheme.
The trigger is straightforward: if a non-construction business spends £3 million or more a year on construction work in any rolling 12-month period, it becomes a deemed contractor. From that point it must register for CIS, verify any subcontractors it pays, make the correct deductions and file monthly CIS300 returns, exactly as a mainstream construction contractor would.
Typical deemed contractors include:
- Property developers and investors who commission large-scale refurbishments or builds.
- Large retailers and supermarkets that run continuous store-fit and maintenance programmes.
- Housing associations and local authorities commissioning repair and maintenance contracts.
- Manufacturers and utilities with ongoing capital works programmes.
The deemed-contractor rule catches businesses that have no CIS expertise and no awareness that the scheme applies to them. The consequence of failing to register and deduct correctly is the same as for any contractor: late-filing penalties on the CIS300, potential penalties for unpaid deductions, and personal liability for directors under HMRC's officer-liability powers.
Once a business qualifies as a deemed contractor, the £3 million test is measured on a rolling 12-month basis. If spend falls below £3 million for a continuous period, HMRC can agree to de-register. In practice many businesses with large property portfolios or capital programmes remain deemed contractors indefinitely.
See deemed contractors explained for the full analysis, including worked examples of the £3 million threshold and registration steps.