Bought or Taken Over a Commercial Building? The 3-Month TM44 Rule Most New Owners Miss

Buying, leasing or taking control of a commercial building comes with a long list of responsibilities.

Solicitors deal with the legal transfer. Facilities teams look at maintenance contracts. Property managers check fire safety records, EPCs, service history and insurance documents.

But one important air-conditioning compliance issue can easily be missed during the handover:

the TM44 inspection report.

For qualifying air-conditioning systems, a change in who controls the system can create an important compliance deadline if the existing inspection report is not handed over.

Government guidance states that where control of an air-conditioning system passes to another person and that new operator has not been given the existing air-conditioning inspection report, the system must be inspected within three months of the new operator taking control.

That makes TM44 more than something to think about every five years.

It can also become an immediate property-handover issue.

For buyers, tenants, landlords, facilities managers and managing agents, understanding this point is important because the responsibility can effectively arrive with the building.

This guide explains what the three-month rule means, who may be responsible, what documents should be requested during a property handover, and what to do if the existing TM44 report cannot be located.

What Is the TM44 3-Month Rule?

Most businesses familiar with TM44 know the basic rule.

Air-conditioning systems with a combined effective rated output of more than 12kW generally require inspection at intervals not exceeding five years. Government guidance confirms that qualifying systems fall within the air-conditioning inspection regime.

What is less widely understood is what can happen when responsibility for the system changes.

Government guidance states that the person controlling the operation of the air-conditioning system must:

• Ensure the required inspection has been carried out.

• Keep the most recent air-conditioning inspection report.

• Give the report to the person taking over responsibility for control of the system.

If control passes to someone new and that person has not been provided with an existing inspection report, the government guidance states that the system must be inspected within three months of the new operator taking control.

This is the crucial point.

The rule is not simply:

“Buy a building and automatically obtain a new TM44 inspection.”

It is more precise than that.

The issue arises where:

• Control of the air-conditioning system transfers to a new person.

• The system falls within the TM44 inspection requirements.

• The new operator has not been provided with the relevant existing air-conditioning inspection report.

That distinction matters.

A valid existing report may already satisfy the requirement until its normal expiry date.

But if the report is missing during the transfer of responsibility, the incoming operator should not simply assume that compliance exists somewhere in the background.

Why Commercial Property Buyers Often Miss This

Commercial property transactions involve enormous quantities of information.

A typical acquisition or lease handover can include:

• EPC documentation.

• Fire risk assessments.

• Asbestos information.

• Electrical inspection records.

• Gas safety documentation.

• O&M manuals.

• Planned preventative maintenance records.

• F-Gas documentation.

• HVAC maintenance contracts.

• Asset registers.

• Building management system information.

• Landlord and tenant responsibilities.

• Service charge records.

TM44 can disappear among those documents.

This is especially common because air-conditioning maintenance records can create a false sense of security.

A buyer or facilities manager might see evidence showing that the air-conditioning has been serviced every year and conclude that everything relating to the system is compliant.

But routine maintenance and TM44 are not the same thing.

We explain this distinction in detail in our guide to PPM contracts versus TM44 compliance.

A maintenance company may have serviced, repaired and inspected equipment for operational purposes without a statutory air-conditioning energy inspection having been completed and lodged.

Equally, an F-Gas inspection does not replace a TM44 inspection.

The different obligations can overlap operationally, but they serve different regulatory purposes.

That is why TM44 should have its own line on any commercial property acquisition or handover checklist.

Who Is Actually Responsible for TM44?

This is where the subject becomes more important than simply asking who owns the building.

Government guidance focuses on the person who controls the operation of the air-conditioning system.

Importantly, this does not simply mean someone who can alter the thermostat.

The government describes control in terms of responsibility for the technical functioning of the system, rather than somebody whose role goes no further than adjusting temperatures or controls.

Depending on the property arrangements, the responsible party could therefore potentially be:

• The freeholder.

• A commercial tenant.

• An occupier.

• A facilities-management organisation.

• A property company.

• A party with contractual responsibility for operating the building services.

The contractual arrangements matter.

For example, imagine a multi-let commercial building.

The landlord may control the central cooling plant serving common areas and multiple floors.

Individual tenants may separately control supplementary split systems installed inside their own demise.

There may therefore be more than one operational arrangement to understand.

This is why simply asking:

“Who owns the building?”

may not answer the TM44 responsibility question.

A more useful question is:

“Who has control of the technical operation of the qualifying air-conditioning system?”

We examine these distinctions further in our guide to TM44 legal responsibility for landlords, tenants and managing agents.

The Property Has Changed Hands — What Should Be Requested?

When a commercial property changes owner, tenant or operator, the incoming party should request the existing air-conditioning compliance documentation as part of the handover.

For TM44 purposes, useful information includes:

• The latest Air Conditioning Inspection Report.

• The date of the previous inspection.

• The report reference or certificate information.

• Details of the accredited assessor.

• Evidence of government lodgement where available.

• Air-conditioning asset register.

• Make and model information.

• Cooling capacities.

• Number of indoor and outdoor units.

• VRF or VRV system details.

• Chiller information.

• AHU and ventilation information where relevant.

• System schematics.

• Maintenance history.

• F-Gas records.

• Details of any equipment added or removed since the previous assessment.

This information does two things.

First, it helps establish whether there is already a valid TM44 report.

Second, it helps determine whether the air-conditioning system currently installed is materially the same system that was assessed previously.

That second point is important.

Buildings change.

Tenants install new units.

Landlords refurbish floors.

VRF systems are extended.

Old condensers are removed.

Server rooms receive new cooling.

Retail tenants install supplementary systems.

Plant can therefore look very different five years after a report was originally produced.

A property may technically have a historic report on file while the actual installed system has changed considerably.

That is why an accurate air-conditioning asset register for TM44 inspections can be extremely valuable.

What If the Seller Says, “There Should Be a TM44 Somewhere”?

That is not the same as receiving the report.

This is one of the most common practical problems in building compliance.

Someone remembers an inspection.

A previous facilities manager believes one was completed.

An old maintenance contractor says an assessor attended.

A certificate may once have been emailed to a member of staff who has now left.

But nobody can actually produce the document.

From the incoming operator’s perspective, that uncertainty should be resolved rather than ignored.

The first steps should normally be:

• Search the property compliance files.

• Ask the outgoing owner or operator directly for the latest report.

• Review historical emails and maintenance records.

• Check whether a report or certificate can be identified through available register information.

• Confirm the installed air-conditioning capacity.

• Establish when control of the system transferred.

TM44.uk provides a TM44 Checker that can help businesses investigate their current position.

If there is still no satisfactory evidence of an existing report, specialist advice should be obtained promptly.

This becomes particularly important where the three-month period following transfer of control is already running.

A Building Purchase Does Not Automatically Reset the Five-Year Clock

This is another important distinction.

Suppose a commercial building has a valid inspection completed two years before it is sold.

The new owner receives the valid report as part of the handover.

A change of ownership does not necessarily mean another inspection must immediately be commissioned simply because the property changed hands.

The existing report remains highly relevant.

The issue is whether the incoming responsible person has been properly provided with the report and whether it remains applicable to the system being operated.

Contrast that with another situation.

A company acquires a building with a substantial VRF installation.

The seller cannot produce an Air Conditioning Inspection Report.

The buyer takes operational control of the system.

That is precisely the type of scenario where the three-month rule becomes important.

This makes documentation during due diligence critical.

We have previously covered the wider acquisition perspective in our article about TM44 commercial property investor due diligence.

The three-month rule adds another layer:

TM44 should be checked before completion wherever possible, not discovered several months afterwards.

Example: Office Acquisition With No TM44 Report

Consider a fictional example.

A property investment company purchases a three-storey office building.

The site contains:

• Four VRF outdoor systems.

• Forty-eight indoor fan-coil units.

• Two supplementary split systems.

• Mechanical ventilation.

The building has been serviced regularly.

The seller supplies maintenance records and F-Gas documentation but no TM44 report.

The buyer completes the acquisition and its facilities team takes responsibility for operating the plant.

Several weeks later, the new facilities manager notices there is no Air Conditioning Inspection Report in the compliance folder.

The mistake would be to say:

“The air conditioning works and it is serviced, so we will deal with TM44 next year.”

The correct approach is to establish the compliance position immediately.

If control has passed and the previous operator has not provided the required report, the three-month rule may be relevant.

This is exactly why TM44 should form part of post-acquisition compliance mobilisation.

Example: New Commercial Tenant Takes an Entire Building

Now consider another scenario.

A company signs a lease on an office building and becomes responsible for the operation and maintenance of the building’s air-conditioning system.

The previous occupier leaves behind O&M manuals but no TM44 report.

The new tenant assumes that TM44 remains the landlord’s responsibility.

That assumption may be wrong.

Responsibility depends on who actually controls the operation of the system and on the contractual arrangements surrounding the property.

If the tenant has assumed technical control of the system, it needs to establish whether the system requires inspection and whether a valid report has been transferred.

This is particularly important with full repairing and insuring leases or arrangements where the occupier takes substantial responsibility for building services.

The lease should therefore be read alongside the actual operational arrangement.

Example: Managing Agent Changes but the Property Owner Does Not

A transfer of responsibility can also occur without the building being sold.

Imagine that a landlord changes managing agents.

The outgoing managing agent has historically maintained the building compliance records.

The incoming agent receives:

• EPC.

• Fire documents.

• Maintenance contracts.

• Insurance information.

But no Air Conditioning Inspection Report.

The new agent should not simply assume that the report exists because the previous agent was managing the site.

Instead, TM44 should be reconciled during mobilisation.

For managing agents overseeing dozens or hundreds of properties, these gaps can multiply quickly.

We discuss the wider portfolio problem in our guide to TM44 compliance for managing agents and property portfolios.

For large portfolios, the best practice is not to treat TM44 as an individual building problem.

It should be maintained within a central compliance register showing:

• Property.

• Responsible person.

• Installed cooling capacity.

• Last inspection date.

• Report reference.

• Expiry date.

• Assessor.

• Current status.

• Outstanding actions.

• Next inspection due date.

That creates auditability and dramatically reduces the chance of certificates disappearing during staff, tenant or managing-agent changes.

What Counts Towards the 12kW Threshold?

Another frequent misunderstanding occurs when someone inspects each unit individually.

A building might contain four wall-mounted split systems rated at 4kW each.

A manager might look at them and say:

“None of our units is above 12kW, so TM44 does not apply.”

That reasoning can be incorrect.

The effective rated output of relevant air-conditioning systems needs to be considered according to the regulatory framework, and multiple units under common control can bring the system above the threshold.

Government guidance confirms that air-conditioning systems with an effective rated output of more than 12kW fall within the inspection regime.

If there is uncertainty, use our TM44 kW Checker or read our guide explaining the TM44 12kW threshold.

This is especially relevant after taking over older commercial buildings because the system may have expanded gradually.

One office might have started with two split systems.

Over ten years, another six could have been installed.

Nobody ever stepped back and calculated the total effective rated output.

The property changes hands, and the new operator inherits a system that has quietly moved into TM44 territory.

Do Recently Installed Air-Conditioning Systems Still Matter?

Yes.

A newly installed air-conditioning system is not permanently outside the TM44 regime simply because it is new.

Government guidance provides for qualifying systems to be inspected at the applicable intervals, with the regulatory framework requiring regular inspection of systems over the threshold.

When acquiring a property containing relatively new HVAC equipment, therefore, ask:

• When was it commissioned?

• Was it installed as one project or expanded in stages?

• What is its effective rated output?

• Has an inspection already been completed?

• Is there a report?

• Has the system been materially altered since the report?

The assumption that “new equipment equals no TM44 issue” can create another documentation blind spot.

Our guide to new air-conditioning installations and TM44 inspections explains this issue in more detail.

What If the Building Has Been Refurbished?

Commercial refurbishment is another point where inherited documentation should be treated carefully.

Imagine purchasing an office where the previous owner carried out a major refurbishment two years earlier.

The old TM44 report may relate to:

• A previous chiller.

• Different indoor units.

• A different zoning arrangement.

• Fewer air-conditioning systems.

• Different controls.

• An earlier building layout.

The existence of an old PDF does not automatically mean the current installation is adequately represented by it.

Any substantial change to the air-conditioning arrangement should prompt a review of the current compliance position.

This is particularly relevant where:

• Floors have been subdivided.

• New tenants installed their own systems.

• Cooling capacity increased.

• Central plant was replaced.

• Controls were substantially altered.

• Extensions were added.

• Server rooms or specialist areas gained dedicated cooling.

Read our detailed guide to TM44 risk after commercial refurbishment for this specific scenario.

Why an Asset Register Can Be More Valuable Than People Expect

One of the best pieces of information a new property owner can inherit is a reliable HVAC asset register.

A good register may include:

• Equipment reference.

• Manufacturer.

• Model.

• Serial number.

• Location.

• Cooling capacity.

• System association.

• Installation date.

• Refrigerant.

• Indoor and outdoor unit relationships.

• Maintenance status.

• Operational status.

This allows an assessor or facilities manager to quickly understand the installation.

Without an asset list, information often needs to be reconstructed physically during a site visit.

That does not necessarily prevent a TM44 inspection, but it can make the assessment more involved.

We regularly encounter buildings where:

• Equipment has no consistent labelling.

• Plant schedules are outdated.

• Indoor units cannot easily be matched to outdoor systems.

• Old equipment remains on registers despite having been removed.

• New equipment has been installed but never added to records.

• Different contractors maintain different parts of the site.

A property takeover is an ideal time to correct these issues.

Even if a valid TM44 report exists, the new owner or operator should understand what equipment it has actually inherited.

Do Not Confuse the TM44 Report With the TM44 Recommendations

A TM44 inspection is not simply about obtaining a piece of paper.

The Air Conditioning Inspection Report is intended to provide the owner or manager with information about the efficiency of the air-conditioning systems they control and identify opportunities to reduce energy use and operating costs.

That creates another opportunity during acquisition.

When the existing report is handed over, do not just check the date.

Read it.

There may be useful recommendations relating to:

• Control settings.

• Operating hours.

• Simultaneous heating and cooling.

• System sizing.

• Maintenance.

• Condenser cleanliness.

• Filters.

• Sensors.

• Zoning.

• Building cooling loads.

• Replacement opportunities.

A buyer might inherit not only the air-conditioning system but also years of unresolved inefficiency.

Our guide to TM44 report recommendations explains how these findings should be interpreted.

For asset managers, this can be especially useful.

TM44 recommendations may help distinguish between:

• Immediate compliance matters.

• Low-cost operational improvements.

• Maintenance issues.

• Recommissioning opportunities.

• Longer-term capital replacement.

That can feed directly into the first-year building management plan.

TM44 Should Be Part of Technical Due Diligence, Not an Afterthought

Commercial due diligence often concentrates heavily on high-value building risks.

Roof condition.

Structure.

Plant life expectancy.

Electrical infrastructure.

Fire safety.

Asbestos.

Dilapidations.

Those are obviously important.

But statutory documentation should sit alongside them.

TM44 is particularly easy to overlook because it concerns equipment that appears to be operational.

A chiller that has failed attracts attention immediately.

A missing inspection report does not.

Nothing flashes red on the BMS.

The building continues cooling.

Occupiers continue working.

The compliance gap can therefore remain invisible.

That is why sophisticated property buyers should include TM44 in their technical due diligence request list before completion.

A simple question can prevent months of uncertainty:

“Please provide the latest Air Conditioning Inspection Report for every qualifying air-conditioning system under the seller’s control.”

If the answer is:

“Not available,”

that is useful information before the transaction completes.

It gives the buyer time to establish the position and plan accordingly.

What Should Solicitors and Property Professionals Ask For?

Property solicitors are not expected to perform HVAC engineering assessments.

But the documentation request itself can be simple.

Where a commercial property contains substantial air conditioning, the due-diligence process should establish:

• Whether a TM44 inspection is required.

• Whether a valid report exists.

• When the last inspection occurred.

• Whether the report will be transferred to the incoming responsible person.

• Who currently controls the system.

• Who will control it after completion.

• Whether the system has materially changed since the report.

For complex transactions, the legal allocation of obligations and the practical control of the system should be considered together.

This is particularly relevant where several parties are involved:

• Freeholder.

• Head tenant.

• Subtenant.

• Managing agent.

• FM contractor.

• Mechanical contractor.

The person paying the electricity bill is not automatically the same as the person with responsibility for technical operation.

Likewise, the person who owns the equipment may not necessarily be the only party relevant to determining operational control.

What Should Facilities Managers Do During Mobilisation?

For facilities managers taking over a new building, TM44 should appear on the mobilisation plan from day one.

A practical sequence is:

• Establish who controls each air-conditioning system.

• Obtain the latest Air Conditioning Inspection Report.

• Verify the report date.

• Check that the property address and system details correspond with the current building.

• Compare the report against the current asset register.

• Identify equipment installed after the inspection.

• Confirm total effective rated output.

• Record the next inspection due date.

• Store the report centrally.

• Add renewal reminders well before expiry.

• Escalate immediately if no valid report can be located.

This is straightforward compliance governance.

Yet it solves one of the biggest recurring weaknesses in property management: knowledge disappearing every time people change.

A good compliance system should survive the departure of:

• The facilities manager.

• The property manager.

• The landlord’s representative.

• The maintenance contractor.

• The tenant.

The record should belong to the building’s compliance process, not to somebody’s inbox.

What About Multi-Site Acquisitions?

The risk becomes much larger when a company acquires an entire portfolio.

Imagine buying:

• 40 retail units.

• 25 offices.

• 12 warehouses.

• 8 leisure sites.

Some locations may not require TM44.

Others may have valid reports.

Some may have expired reports.

Others may have no documentation at all.

Treating these sites individually can become chaotic.

Instead, create a compliance triage.

Priority 1 — No TM44 information

Determine cooling capacity and responsibility immediately.

Priority 2 — Report exists but appears expired

Verify the inspection date and arrange renewal where required.

Priority 3 — Valid report but building has changed significantly

Compare the current installation with the inspected system.

Priority 4 — Valid report and unchanged system

Record the report and renewal date.

Priority 5 — Clearly below the relevant threshold

Document why the site is considered outside the inspection requirement and retain supporting information.

For organisations handling large estates, our TM44 portfolio management service is designed around this type of centralised approach.

Can You Check Whether a TM44 Certificate Already Exists?

Sometimes.

The availability and searchability of records can vary, and the safest approach is to gather as much identifying information as possible.

Useful details include:

• Full property address.

• Postcode.

• Building name.

• Previous business or occupier name.

• Approximate date of inspection.

• Previous assessor details.

• Certificate or report reference.

TM44.uk’s TM44 Register guidance explains how the register fits into the compliance process.

Our TM44 Checker can also help establish whether further investigation is required.

However, do not allow an unsuccessful search to become an excuse for indefinite delay.

If the incoming operator has not been given the required report, the three-month requirement may be relevant.

What Happens During a New TM44 Inspection?

If a new inspection is required, an accredited air-conditioning energy assessor reviews the qualifying system and its operation.

Depending on the system and building, this can involve examination of:

• Installed equipment.

• Cooling capacity.

• System configuration.

• Controls.

• Maintenance arrangements.

• Indoor and outdoor units.

• Air distribution.

• Ventilation interaction.

• Operating conditions.

• Energy-efficiency opportunities.

• System sizing.

• Available records.

The assessment is not the same as destructive testing or a repair visit.

Its purpose is to assess the air-conditioning system from an energy-performance and compliance perspective.

For a full explanation, see what happens during a TM44 inspection.

You can also review our main TM44 air-conditioning inspection service for the overall process.

What Information Helps Us Quote a TM44 Inspection?

If you have recently taken over a commercial building and need a quotation, the process can usually be accelerated by providing basic information.

The most useful starting points are:

• Full site address and postcode.

• Building type.

• Approximate floor area.

• Number of floors.

• Number of air-conditioning units.

• Equipment makes and models where known.

• Cooling capacities where available.

• Asset register.

• Previous TM44 report if one exists.

• Maintenance records.

• Details of chillers, VRF/VRV systems, splits and packaged units.

• Details of AHUs or associated mechanical ventilation.

• Site access restrictions.

• Required completion date.

Do not worry if some of this information is unavailable.

We frequently deal with inherited buildings where the documentation is incomplete.

Our guide on what we need for a TM44 quotation explains the information in more detail.

The Biggest Mistake: Waiting Until the Next Compliance Audit

A common pattern looks like this:

A company acquires a property.

Nobody asks about TM44.

Twelve months later, a compliance audit takes place.

The auditor asks for the Air Conditioning Inspection Report.

The facilities team searches its records.

Nothing can be found.

The previous owner’s facilities manager has left.

The old managing agent no longer works on the building.

Nobody knows which contractor performed the previous assessment.

At that point, what could have been resolved during handover has become a retrospective investigation.

The three-month transfer rule is precisely why this approach is risky.

The better process is simple:

Check TM44 when control changes, not when somebody eventually asks for the certificate.

Treat TM44 Like a Building Asset, Not Just a Certificate

A strong commercial property compliance system should treat the TM44 report as part of the building’s permanent technical record.

That means the report should move with responsibility for the air-conditioning system.

It should not exist only:

• In an old contractor’s email.

• On a former employee’s laptop.

• In an inaccessible SharePoint folder.

• Inside a forgotten property-management portal.

• With the previous tenant.

The incoming operator should be able to identify the latest report, understand when renewal is due and confirm what system was actually assessed.

This creates better compliance.

It also creates better property management.

A Better Commercial Property Handover Standard

For organisations that regularly buy, lease or manage commercial buildings, we recommend adding a specific air-conditioning compliance section to the standard handover checklist.

It should contain:

TM44 / Air Conditioning Inspection Report

• Report received: Yes / No.

• Inspection date.

• Expiry or next inspection date.

• Report reference.

• Assessor details.

• Qualifying system confirmed.

• Current cooling capacity.

• Asset register received.

• Material system alterations since inspection: Yes / No.

• Incoming responsible person identified.

• Further action required.

This takes minutes to complete.

But it creates an auditable record that can prevent the issue from disappearing between departments.

Why This Matters Beyond Legal Compliance

TM44 should not be viewed purely through the lens of avoiding enforcement.

Commercial property owners spend substantial sums operating cooling systems.

An inefficient system can waste energy every day for years.

An inspection can identify opportunities involving controls, operation, maintenance and system performance.

The government’s own post-implementation review describes Air Conditioning Inspection Reports as a tool intended to provide owners and managers with information about system efficiency and opportunities to reduce energy use and operating costs.

That makes the acquisition of a commercial building a particularly sensible moment to review the system.

You are already examining:

• Operating budgets.

• Service contracts.

• Planned maintenance.

• Capital expenditure.

• Energy performance.

Adding air-conditioning efficiency to that process is logical.

A buyer could therefore turn what initially appears to be a compliance obligation into part of a wider first-year efficiency strategy.

Recently Taken Over a Commercial Property? Do This Now

If you recently bought, leased or assumed responsibility for a commercial building with air conditioning, do not wait for the next annual compliance review.

Check the position now.

Start with four questions:

• Is the combined air-conditioning capacity likely to exceed 12kW?

• Who controls the technical operation of the system?

• Have you actually received the latest Air Conditioning Inspection Report?

• When was the system last inspected?

If the answer to the third question is no, investigate immediately.

Where control has passed to a new operator and the previous operator has not supplied the existing inspection report, government guidance states that the system must be inspected within three months of the new operator taking control.

That is the part of the TM44 rules commercial property buyers and incoming occupiers cannot afford to overlook.

Nationwide TM44 Inspections for Commercial Property Owners

TM44.uk provides air-conditioning inspections for commercial properties across the UK.

We work with:

• Commercial landlords.

• Property investors.

• Facilities managers.

• Managing agents.

• Corporate occupiers.

• Retail businesses.

• Hotels.

• Offices.

• Industrial and mixed-use properties.

• Multi-site organisations.

If you have recently acquired or taken responsibility for a property and cannot locate the existing TM44 report, send us the site details.

We can review the information available, help establish the likely inspection requirement and provide a quotation where a new assessment is required.

You can request a TM44 quotation or use our TM44 Checker if you are unsure of the property’s current position.

The important thing is not to assume that a missing report is somebody else’s problem.

When control of the air-conditioning system changes, the compliance responsibility can change with it.

And in the right circumstances, the clock may already be running.