Property developers, landlords and property investment companies can all be affected by the Construction Industry Scheme (CIS), but the rules depend on what the business actually does, not simply how much it spends on building work.

By Steve Bicknell FCMA, CGMA

A landlord might spend £250,000 refurbishing rental properties without becoming a CIS contractor. Another company could spend considerably less developing a building and be required to operate CIS from its first relevant subcontractor payment.

This distinction creates uncertainty for buy-to-let investors, property developers, HMO operators, serviced accommodation businesses and companies converting commercial buildings into residential accommodation.

One of the most common misconceptions is that CIS only applies when construction expenditure exceeds £3 million.

That is incorrect for businesses undertaking property development.

The £3 million threshold applies to deemed contractors. A mainstream property developer may have CIS obligations regardless of the amount spent.

But what happens when an ordinary property investor undertakes substantial refurbishment? Does converting houses into HMOs amount to development? Is there a monetary threshold for substantial works?

This guide examines the rules, HMRC guidance, practical examples and the risks of getting CIS registration wrong.

1. What is the Construction Industry Scheme?

The Construction Industry Scheme is administered by HM Revenue & Customs (HMRC) and governs certain payments made by contractors to subcontractors for construction operations.

Where CIS applies, contractors are normally required to:

• Register with HMRC as a CIS contractor.
• Establish whether the work is within the scheme.
• Verify subcontractors with HMRC when required.
• Make the correct deductions from subcontractor payments.
• Provide payment and deduction statements.
• Submit monthly CIS returns.
• Pay CIS deductions to HMRC.

The standard deduction rates are:

Subcontractor status	CIS deduction
Registered and verified for payment under deduction	20%
Not registered or not successfully matched for the standard rate	30%
Approved for gross payment status	0%

CIS deductions are generally calculated on the relevant payment excluding VAT and allowable direct materials costs.

They are advance payments towards the subcontractor’s tax liabilities, rather than necessarily representing the final tax payable.

A business can be both a contractor and a subcontractor.

For example, a building company might receive payments from a property developer while making its own payments to electricians, plumbers and other subcontractors.

2. Mainstream contractors versus deemed contractors

For property businesses, the most important distinction is between mainstream and deemed contractors.

Mainstream contractors

A mainstream contractor is a business whose activities include construction operations.

This can include:

• Building contractors.
• Property developers.
• Speculative builders.
• Businesses undertaking substantial property development.
• Companies established to develop and sell properties.

Mainstream contractors do not benefit from the £3 million deemed-contractor threshold.

A property development company undertaking its first project may therefore need to register for CIS before paying its first subcontractor.

Deemed contractors

A deemed contractor is a business that is not otherwise a mainstream construction contractor but whose expenditure on construction operations exceeds the statutory threshold.

This category can include:

• Property investment companies.
• Large residential landlords.
• Commercial landlords.
• Retailers.
• Manufacturers.
• Other non-construction businesses commissioning significant construction work.

The deemed-contractor threshold is more than £3 million of construction expenditure over a rolling 12-month period.

The classification of the business is therefore essential.

A property investment company is not automatically a mainstream contractor simply because it employs builders.

However, it can become one if its activities amount to property development.

3. How does the £3 million CIS threshold work?

The £3 million threshold applies to businesses that are not already mainstream contractors.

It is assessed by reference to construction expenditure over a rolling 12-month period, not simply expenditure in the company’s accounting year.

Example: a large property investment company

ABC Property Investments Ltd owns a portfolio of residential and commercial rental properties.

During a rolling 12-month period, it incurs the following expenditure:

Construction work	Amount
Roof replacements	£650,000
Kitchen and bathroom refurbishments	£750,000
Structural repairs	£850,000
Heating and electrical installations	£500,000
Other construction operations	£400,000
Total	£3,150,000

Assuming ABC remains a property investment business rather than undertaking development, it exceeds the deemed-contractor threshold.

It must consider its CIS registration and compliance obligations.

The company should not wait until its financial year-end to assess whether it has crossed the threshold.

Does spending £3 million automatically mean CIS applies?

Not every payment relating to property is necessarily expenditure on construction operations.

Professional fees, property acquisition costs and other expenditure must be analysed according to the relevant CIS rules.

The business should maintain a record of qualifying construction expenditure so that the threshold can be monitored.

Can a deemed contractor deregister?

A deemed contractor whose construction expenditure falls below the threshold may be able to cease operating CIS, subject to the applicable rules and HMRC agreement.

It should not simply stop making deductions or submitting returns without resolving its contractor status.

4. When does a property investor become a property developer?

This is one of the most important issues for landlords and property companies.

HMRC’s guidance at CISR12080 recognises that property investors can undertake construction work without automatically becoming mainstream contractors.

For example, a landlord may need to:

• Replace roofs.
• Refurbish kitchens and bathrooms.
• Upgrade electrical installations.
• Install fire safety systems.
• Improve insulation.
• Undertake structural repairs.
• Bring properties into compliance with building regulations.

These activities can be consistent with managing and maintaining an investment portfolio.

However, a property investor can become a mainstream contractor when its activities move into property development.

HMRC identifies the construction of new buildings and redevelopment involving a change in the nature or use of a building as particularly relevant examples.

Example: an office building converted into flats

XYZ Property Holdings Ltd purchases an office building and plans to convert it into eight residential apartments.

The construction work costs £450,000.

The company intends to retain the completed flats as rental investments.

Although the company will ultimately receive rental income, the project involves a substantial change in the building’s use.

HMRC’s guidance indicates that this type of redevelopment can bring a property investment business within CIS as a mainstream contractor.

The company should therefore assess its CIS obligations before making payments under construction contracts.

The fact that the completed property will be retained for investment does not automatically prevent the development works from falling within CIS.

5. What counts as substantial works for CIS?

There is no statutory monetary threshold defining substantial works for the purpose of deciding whether a property investor has become a mainstream contractor.

Spending £100,000, £250,000 or even £500,000 does not, by itself, answer the question.

Equally, expenditure below £3 million does not protect a business that is actually undertaking property development.

The key issue is whether the works form part of ordinary property investment activities or whether the business is carrying on property development.

Factors to consider

A CIS review should consider:

1. Nature of the work: Are the works repairs, refurbishment, conversion, reconstruction or new construction?
2. Purpose: Are they intended to maintain and improve an investment or create a substantially different property?
3. Change in use: Does the building move from one type of use to another?
4. Scale: How extensive are the works relative to the property and the business?
5. Frequency: Is this an occasional refurbishment or part of a recurring development programme?
6. Business activities: Is the company primarily holding investments or regularly undertaking development?
7. Contracts: Which entity commissions and pays for the construction operations?

No single factor necessarily determines the outcome.

Is a change of use essential?

No. A change in the nature or use of a building is an important indicator in HMRC’s guidance, but it should not be treated as the only possible route to mainstream contractor status.

A business repeatedly undertaking substantial construction projects may need closer examination even where the completed properties remain within the residential sector.

Conversely, a significant refurbishment does not automatically become property development simply because it is expensive or involves structural work.

The correct assessment is based on the facts and the company’s actual business activities.

6. Worked example: £269,000 spent converting four residential properties into HMOs

Consider a limited company that owns four residential rental properties.

The company spends £269,000 refurbishing and adapting the properties to meet House in Multiple Occupation (HMO) requirements.

The works are intended to maximise rental income and ensure the properties comply with the relevant HMO requirements.

Before the work, the properties were residential.

After the work, they remain residential, although they are now operated as HMOs.

The company intends to retain the properties for rental income.

Does the company need to register for CIS?

Not necessarily.

This scenario was considered in specialist advice obtained for a comparable property investment company.

The conclusion was that the company could remain outside CIS where:

• It was genuinely operating as a property investor.
• The works were consistent with refurbishment of existing residential investments.
• The properties remained in residential use.
• The company was not otherwise undertaking property development activities.
• Relevant construction expenditure remained below the deemed-contractor threshold.

The £269,000 expenditure did not itself make the company a mainstream contractor.

Why is the HMO distinction important?

A conversion from an ordinary residential letting arrangement to HMO accommodation may involve considerable expenditure.

Typical works might include:

• Additional bathrooms.
• Fire doors and fire detection systems.
• Electrical upgrades.
• Alterations to internal layouts.
• Improved kitchens and communal facilities.
• Building regulation compliance.

However, the properties may continue to be used for residential accommodation.

That is different from converting an office block into residential flats, where there is a clear change from commercial to residential use.

Does residential-to-residential mean CIS can never apply?

No.

This is an important qualification.

A property remaining residential is relevant evidence, but it is not a blanket CIS exemption.

For example, demolishing an existing house and constructing a new block of apartments could amount to property development even though the site was residential before and afterwards.

Similarly, repeated major redevelopment projects might indicate that the company is carrying on development activities rather than merely maintaining investments.

The £269,000 HMO example therefore illustrates a possible outcome, not a universal rule for all HMO conversions.

Practical conclusion

An investment company refurbishing existing residential properties into HMOs may remain outside CIS where the work is consistent with its investment activities and it does not meet the deemed-contractor threshold.

However, the facts should be documented before relying on that conclusion.

7. What do the tax tribunals tell us?

The distinction between property investment and development has been considered in tribunal cases.

Thornton Heath LLP v HMRC

The Thornton Heath LLP decision is an important example of a property investment business successfully challenging HMRC’s position on CIS.

The case demonstrates that substantial building work does not automatically make a property investor a mainstream contractor.

The tribunal considered the business’s actual activities and circumstances.

It is therefore unsafe to assume that every major refurbishment triggers CIS.

Kalinga Holdings Ltd v HMRC (2026)

The more recent Kalinga Holdings Ltd decision illustrates the risks of relying on the £3 million threshold without properly examining mainstream contractor status.

The case concerned significant construction payments and the company’s understanding of its CIS obligations.

The practical lesson is that a business should investigate and document its contractor status rather than assume that expenditure below £3 million means CIS cannot apply.

What can landlords learn from these cases?

The cases illustrate why the analysis is fact-sensitive.

The following questions are particularly important:

• Is the company genuinely an investor?
• What is the nature of the building project?
• Has the business moved into development activities?
• Is the company relying on the £3 million threshold without first considering mainstream contractor status?
• Has the company obtained and retained appropriate advice?

A documented assessment can be especially valuable if HMRC later challenges the treatment.

8. Do property flippers need to register for CIS?

Property flipping typically involves buying properties, improving them and selling them for profit.

Where a business systematically acquires properties for renovation, conversion or redevelopment, it may be carrying on property development activities.

That can make it a mainstream contractor.

Example

A company purchases a run-down property and engages subcontractors to:

• Reconfigure the internal layout.
• Undertake structural alterations.
• Install new plumbing and electrical systems.
• Extend the building.
• Prepare it for resale.

The company should consider whether it is operating as a property developer and whether CIS applies to payments to subcontractors.

A straightforward purchase and resale without construction work does not automatically create CIS obligations.

But a business regularly undertaking development projects should not assume that it is exempt because it describes itself as a property investor.

For further discussion, see:

Do Property Flippers and Investors Need to Do CIS?

9. Does CIS apply to ordinary buy-to-let landlords?

Most smaller buy-to-let landlords carrying out routine repairs and maintenance will not become CIS contractors solely because they employ builders.

For example, an individual landlord owning three rental properties who spends £25,000 replacing a roof will not ordinarily become a mainstream contractor merely because of that expenditure.

However, CIS needs consideration where:

• The landlord undertakes substantial development or conversion work.
• The business carries out repeated development projects.
• Construction expenditure exceeds the deemed-contractor threshold.
• The business operates through a company established for property development.
• Investment and development activities are combined.

Private householders versus landlords

A private individual paying a builder to work on their own home is normally outside CIS under the private-householder exclusion.

A landlord commissioning work on a rental property does not automatically qualify for that exclusion.

The landlord may still be outside CIS, but the reason is generally that they are neither a mainstream nor a deemed contractor.

The distinction matters because work on residential property is not automatically exempt from CIS.

10. HMOs, serviced accommodation and commercial-to-residential conversions

Different property projects can produce different CIS outcomes.

Project	Typical CIS consideration
Routine refurbishment of a buy-to-let property	Usually consistent with property investment
Upgrading an existing HMO to meet regulations	May remain investment refurbishment
Converting a residential house into an HMO	Depends on the scale and nature of the works
Converting offices into residential flats	Strong indicator of property development
Building new houses for sale	Generally mainstream property development
Demolishing a house and constructing new apartments	Strong indicator of property development
Furnishing an existing property for serviced accommodation	Not necessarily property development
Converting commercial premises into serviced apartments	May be mainstream property development

The intended use of the completed property is relevant, but it is not the only consideration.

A company that retains newly developed properties for rental income can still have mainstream contractor obligations during development.

11. Do property SPVs need CIS registration?

Property investors and developers frequently establish special purpose vehicles (SPVs) to hold individual properties or developments.

A separate company does not automatically benefit from the CIS registration status of its parent or another group company.

Example: a development SPV

Development SPV Ltd is established to acquire a site and commission the construction of six houses.

The company:

• Has no employees.
• Has never completed a previous development.
• Appoints a main contractor to build the houses.
• Intends to sell the completed properties.

The company may be a mainstream contractor from the outset.

The fact that it has no employees or previous trading history does not prevent CIS from applying.

What about property investment SPVs?

An SPV established to hold a rental property will not automatically be a mainstream contractor.

However, its activities must be considered.

If the company commissions substantial redevelopment or undertakes property development, CIS may apply.

Each legal entity and its contractual arrangements should be reviewed separately.

This is particularly important where a parent company, development manager and property-owning SPV are all involved in the project.

12. What construction operations are covered by CIS?

CIS applies to a broad range of construction operations.

Examples include:

• Construction of new buildings.
• Extensions and structural alterations.
• Building conversions.
• Demolition.
• Site preparation and groundworks.
• Roofing.
• Plumbing and electrical installation.
• Installation of heating and ventilation systems.
• Painting and decorating.
• Certain landscaping and associated site works.
• Repairs and refurbishment.

However, some services can fall outside CIS when supplied separately.

Examples include:

• Architectural services.
• Surveying.
• Professional design and consultancy.
• Supply and delivery of materials without construction work.
• Hire of plant without an operator.
• Certain security system installations.
• Certain floor coverings.

Mixed contracts

Where a contract includes both construction operations and other services, the CIS treatment can extend to payments under the wider contract.

The contract should therefore be reviewed rather than relying solely on how the supplier describes the invoice.

For example, a contract covering building refurbishment together with other associated services may need different treatment from a standalone professional consultancy agreement.

13. How are CIS deductions calculated?

CIS deductions are not necessarily calculated on the full invoice value.

Allowable direct materials costs and VAT are generally excluded from the deduction calculation.

Example: labour and materials

A subcontractor invoices a property developer as follows:

Description	Amount
Labour	£12,000
Direct materials	£8,000
Total excluding VAT	£20,000

Assume the subcontractor is verified at the standard 20% deduction rate and the materials cost is properly supported.

The CIS deduction is:

£12,000 × 20% = £2,400

The payment, before considering any applicable VAT, would be:

£20,000 − £2,400 = £17,600

The contractor must ensure that the materials amount is properly identified and supported.

Inflated materials charges or unsupported deductions can create CIS compliance problems.

See also:

What Counts as Labour Under CIS?

14. What if a property developer appoints a main contractor?

A property developer does not automatically escape CIS by appointing one main contractor to manage the entire project.

For example:

• A development company appoints a building contractor.
• The building contractor appoints electricians, plumbers and roofers.
• The developer pays the building contractor.
• The building contractor pays its subcontractors.

There can be CIS obligations at both levels.

The development company may need to operate CIS on payments to the building contractor.

The building contractor may separately need to operate CIS on payments to its own subcontractors.

If the building contractor has verified gross payment status, the developer may be able to pay it without making a CIS deduction.

However, this does not automatically remove the developer’s CIS registration or reporting obligations.

15. How does CIS interact with VAT domestic reverse charge?

CIS and the VAT domestic reverse charge are separate regimes.

CIS determines whether tax must be deducted from payments to subcontractors.

The VAT domestic reverse charge determines who accounts for VAT on certain construction services.

Where the reverse charge applies, the customer rather than the supplier accounts for VAT.

However, not every payment subject to CIS is also subject to the VAT reverse charge.

Property developers as end users

A property developer commissioning construction services for its own development may qualify as an end user for VAT reverse charge purposes where it is not making an onward supply of those construction services.

Where the end-user exception applies and the appropriate written notification has been provided, the supplier will generally apply the normal VAT rules.

The developer may therefore have CIS obligations even though the supplier charges VAT in the ordinary way.

CIS registration does not automatically mean that the VAT reverse charge applies.

We will explore this distinction in more detail in a separate article.

16. What happens if a property company fails to register for CIS?

Failure to operate CIS correctly can result in significant financial and administrative consequences.

Potential problems include:

• Unpaid CIS deductions.
• Interest and penalties.
• Late or incorrect monthly returns.
• Failure to verify subcontractors.
• Incorrect treatment of materials.
• Missing payment and deduction statements.
• Poor recordkeeping.
• Difficulties reconstructing payments after a development has finished.

HMRC may seek to recover deductions that should have been made.

The fact that a subcontractor has declared its income does not automatically remove the contractor’s liability.

There are specific provisions and potential reliefs concerning failures to deduct, but these depend on the circumstances.

A business discovering historic CIS errors should investigate them promptly and consider how to regularise its position with HMRC.

17. What should landlords and developers do before starting substantial works?

The best time to assess CIS is before signing construction contracts and making payments.

CIS contractor-status checklist

1. Identify the business: Is it a property investor, developer or a combination of both?
2. Review the works: Are they repairs, refurbishment, substantial conversion or new construction?
3. Consider the property’s use: Will the nature or use of the building change?
4. Review project frequency: Is the company undertaking occasional refurbishment or repeated development?
5. Check the £3 million threshold: Monitor construction expenditure over the rolling 12-month period where the business is not mainstream.
6. Identify the contracting entity: Which company is commissioning and paying for the work?
7. Assess CIS registration: Establish whether registration is required before making relevant payments.
8. Verify subcontractors: Obtain the correct HMRC payment status.
9. Review materials and invoices: Ensure deductions are calculated correctly.
10. Check VAT: Determine whether normal VAT or the domestic reverse charge applies.
11. Maintain records: Retain contracts, invoices, subcontractor verifications and the documented CIS assessment.
12. Review changes: Reconsider CIS status if the scale or nature of the project changes.

Where the distinction between investment and development remains uncertain, professional advice or a technical enquiry to HMRC may be appropriate.

18. Frequently asked questions

Does a property developer need CIS registration if construction costs are below £3 million?

Yes, potentially. A mainstream property developer does not benefit from the £3 million deemed-contractor threshold.

Is there a financial definition of substantial works for CIS?

No. There is no fixed monetary amount that automatically turns refurbishment into property development.

Does converting a residential property into an HMO trigger CIS?

Not automatically. A property investment company may remain outside CIS where the work is consistent with its investment activities and the deemed-contractor threshold is not exceeded. However, extensive reconstruction or wider development activity can change the conclusion.

Does CIS apply to landlords carrying out repairs?

Ordinary repairs and maintenance do not automatically make a landlord a mainstream contractor. Large investment businesses must also consider the deemed-contractor threshold.

Does converting offices into flats trigger CIS?

It can. HMRC identifies redevelopment involving a change in the nature or use of a building as an activity that may bring a property investor within mainstream contractor status.

Does a property SPV need CIS registration?

Potentially. A company established to commission property development may be a mainstream contractor even if it has no employees and has never undertaken a previous project.

Does CIS apply when the builder is a limited company?

Yes. Subcontractors can be limited companies, partnerships or sole traders.

What if the subcontractor has gross payment status?

A verified subcontractor with gross payment status can generally be paid without CIS deductions. The contractor may still have registration and reporting obligations.

Can a property investor stop operating CIS after a development finishes?

Potentially. The business should review whether it remains a mainstream or deemed contractor and resolve its position with HMRC before ceasing compliance.

Is CIS the same as VAT reverse charge?

No. CIS concerns tax deductions from subcontractor payments. VAT reverse charge determines who accounts for VAT on certain construction services.

19. Conclusion: substantial works do not automatically mean CIS registration

The Construction Industry Scheme is not restricted to traditional building contractors.

Property developers, speculative builders, landlords and property investment companies can all be affected.

However, the rules distinguish between mainstream property development and ordinary property investment.

A property developer may need CIS registration from its first relevant subcontractor payment, even where construction expenditure is far below £3 million.

A property investor carrying out ordinary refurbishment may remain outside CIS, even where the expenditure is substantial.

The £269,000 HMO example demonstrates why the cost of refurbishment alone does not determine the answer.

The crucial question is whether the company’s activities amount to property development or remain consistent with property investment.

Because the distinction is fact-sensitive, businesses planning major conversions or redevelopment should review CIS before making construction payments.

Need help with CIS registration or property development tax?

At Bicknell Business Advisers Limited, we work with property investors, landlords, developers and construction businesses on their accounting and tax obligations.

We can help with:

• Reviewing whether your property company needs CIS registration.
• Assessing CIS implications of substantial refurbishment and conversions.
• Registering contractors and subcontractors.
• Subcontractor verification and deductions.
• Monthly CIS returns.
• CIS and VAT domestic reverse charge.
• Property development accounts and Corporation Tax.
• Reviewing historic CIS compliance problems.

Contact Bicknell Business Advisers

Telephone: 01202 025252

Website: www.bicknells.net

Further reading

• Do Property Flippers and Investors Need to Do CIS?
• How Do You Register for CIS?
• What Counts as Labour Under CIS?
• How Do You Complete a Monthly CIS Return?
• What If You Fail to Register for CIS?

HMRC guidance and legislation

• Construction Industry Scheme: Guide for Contractors and Subcontractors (CIS340)
• CISR12080 – Property Developers and Property Investment Businesses
• Who Is Covered by CIS?
• Finance Act 2004, sections 57–77 and Schedule 11.

This article provides general information based on legislation and HMRC guidance available in November 2026. The CIS treatment of any project depends on its particular facts, contractual arrangements and business activities. Professional advice should be obtained where the position is uncertain.

About the Author

Steve Bicknell FCMA, CGMA is Managing Director of Bicknell Business Advisers Limited, specialising in property taxation, landlord tax planning, SDLT, Capital Gains Tax and property company structures throughout the UK.