Hillingdon's new additional HMO licensing regime came into force on 24 August 2026, bringing smaller shared properties into a borough-wide licensing framework. For landlords refinancing those properties, this can create a second issue: mortgage lenders may have their own requirements around the licence, planning position and evidence required before completion.
A landlord with an eight-bedroom HMO is unlikely to be surprised when a mortgage lender asks about licensing.
The more important group affected by Hillingdon's latest regulatory change may be landlords who have never thought of their property as a particularly specialist HMO at all.
A house occupied by three or four unrelated tenants sharing a kitchen or bathroom may look, from the owner's perspective, much like an ordinary buy-to-let property. Under Hillingdon's new borough-wide additional licensing regime, however, it can now require an HMO licence.
That distinction matters for more than council compliance. It can also become relevant when the landlord wants to remortgage, raise capital, restructure a portfolio or sell the property to another financed landlord.
A property can be perfectly capable of producing rent and still encounter a refinance problem if the licensing or planning evidence required by the proposed lender is not available when its solicitor is ready to complete.
What Changed in Hillingdon on 24 August?
Hillingdon Council's additional HMO licensing designation now covers the entire London borough.
The designation applies to HMOs occupied by three or more people comprising two or more households, subject to the statutory exclusions and where the property is not already within the nationally prescribed mandatory HMO licensing regime.
Hillingdon's mandatory regime already applies to larger HMOs occupied by five or more unrelated people from two or more households. The additional scheme therefore brings a significant category of smaller shared houses into licensing.
Applications for the new regime opened on 20 May 2026. Hillingdon required landlords to apply and achieve full compliance by 23 August, with enforcement against non-applicant or non-compliant HMOs commencing from 24 August.
The formal designation runs until 23 August 2031 unless the council revokes it earlier.
The Three-Tenant Property Is Where Landlords Can Be Caught Out
The most commercially interesting part of the change is the lower occupancy threshold.
Many professional landlords already understand that large HMOs are subject to a different regulatory and mortgage framework from ordinary single-household buy-to-let.
A three-bedroom house occupied by three unrelated professionals can feel very different. Yet if those occupiers form two or more households and share facilities, the property can fall within Hillingdon's additional licensing designation.
This means the landlord's historic assumption that “my property doesn't need an HMO licence because it has fewer than five tenants” is no longer sufficient in Hillingdon.
Five occupiers remains important for mandatory licensing. It is no longer the relevant threshold for deciding whether every HMO in the borough requires a licence.
Fewer than five occupiers does not necessarily mean no HMO licence. Hillingdon's additional scheme extends licensing to qualifying HMOs with three or four occupiers.
Why Can Licensing Affect an HMO Remortgage?
Mortgage lenders do not all treat licensing in exactly the same way. The underwriting approach can depend on the lender, property, transaction and type of HMO.
However, current published specialist lending criteria demonstrate why landlords should establish the position before beginning a refinance.
InterBay, for example, currently states in its published criteria that for HMO refinance applications its solicitor must receive a copy of the relevant local-authority HMO licence confirming that the borrower is the licence holder before completion. Its criteria state that funds will not be released until the licence has been received.
That does not mean every lender adopts the same policy. It demonstrates something more important: the licence can be a mortgage completion requirement, not simply an administrative matter between landlord and council.
A landlord can therefore have acceptable rental coverage, sufficient equity, a satisfactory valuation and an otherwise suitable mortgage application, yet still encounter a delay during the legal process because the lender's licensing requirement has not been satisfied.
An Application and an Issued Licence May Not Be the Same Thing to a Lender
This distinction becomes particularly important immediately after the introduction of a new licensing regime.
Hillingdon says it aims to process HMO licence applications within 12 weeks. Actual circumstances can vary, and the council needs supporting information including property plans and relevant safety documentation as part of the application process.
Meanwhile, a mortgage lender may have its own requirements over what it will accept before completion.
Evidence that a landlord submitted a licence application is not automatically equivalent to holding the issued licence. Whether an application, undertaking, existing licence or final licence is acceptable depends on the particular lender and transaction.
This is why the issue should be investigated at the mortgage research stage rather than discovered during conveyancing.
A Fixed-Rate Expiry Can Turn a Licensing Delay Into a Finance Problem
Timing becomes particularly important where the landlord already has a mortgage approaching maturity.
Consider a landlord whose fixed rate expires in three months. They may expect to refinance onto another specialist buy-to-let product, release capital and complete before reverting to their existing lender's follow-on rate.
If the property now requires additional licensing and the proposed lender needs the issued licence before releasing funds, the licensing timetable becomes part of the mortgage timetable.
The same issue can arise with a maturing bridge, where the consequences of delay may be more significant.
The practical question is therefore not simply: “Can this HMO be refinanced?”
It is: “Can it be refinanced with the right lender within the time actually available?”
Capital Raising Can Be Affected Too
Hillingdon landlords may also want to refinance for reasons other than securing a new mortgage rate.
A professional landlord may be raising equity from an existing HMO to fund another purchase, refurbishment or portfolio deposit. A limited company may be restructuring debt across several properties. Another investor may be refinancing expensive short-term borrowing following conversion or refurbishment.
In each case, licensing can become relevant to the timing of the capital release.
That matters because the financial consequence may sit elsewhere in the portfolio. If equity from one property is intended to fund the deposit on another acquisition, a delay to the HMO refinance can potentially affect the second transaction too.
Planning and Licensing Are Separate Issues
Hillingdon landlords also need to avoid treating an HMO licence as confirmation that the property's planning position is satisfactory.
They are separate regulatory regimes.
Hillingdon introduced a borough-wide Article 4 Direction in December 2025 affecting changes of use from Class C3 dwellinghouses to Class C4 HMOs. The council states that planning permission is now required before converting a family home into an HMO across the borough.
A property may therefore need both its licensing position and planning history considered.
For a mortgage lender, that distinction can matter because specialist HMO underwriting may involve both licensing and planning checks during the application and legal process.
Landlords should obtain specialist planning or legal advice where the property's lawful use is uncertain. Mortgage advice cannot retrospectively resolve a planning problem.
Before Starting a Hillingdon HMO Refinance, Check:
- How many people currently occupy the property.
- How many households those occupiers form.
- Whether the property falls within additional or mandatory HMO licensing.
- Whether the required licence application has been submitted.
- Whether an HMO licence has actually been issued.
- Who is named as the licence holder.
- The property's planning status and historic use.
- Whether the property meets the relevant licensing conditions and standards.
- The current mortgage balance and fixed-rate or facility expiry.
- Whether capital is being raised as part of the refinance.
- The proposed lender's specific HMO licensing requirements.
Licence Holder and Mortgage Borrower Can Matter
Another detail that should not be overlooked is the identity of the licence holder.
This can become particularly relevant where property ownership has changed, an HMO has moved into a limited company structure, or the landlord is refinancing from personal ownership into an SPV.
Published lender criteria can require the borrower to be identified as the licence holder. That means it is not enough simply to establish that a licence exists for the address.
The ownership, borrowing entity and licensing position need to be considered together.
A landlord contemplating a transfer between personal and corporate ownership should therefore take appropriate tax and legal advice and establish the mortgage and licensing consequences before changing the structure.
Purchasing an HMO Can Be Different From Refinancing One
Specialist lenders can also distinguish between purchases and refinances when applying their HMO licensing criteria.
InterBay's current criteria illustrate this distinction. For purchases of HMOs with up to six bedrooms, its criteria provide for circumstances in which the applicant can undertake to obtain a valid licence in their own name after completion. Its refinance criteria are different and require the local-authority licence before funds are released.
Again, that is one lender's published approach rather than a universal market rule.
But it shows why a landlord should not assume that because they previously bought an HMO without an issued licence in their own name, the same approach will necessarily work when they later refinance it.
Why This Matters for Portfolio Landlords
The regulatory change can also affect landlords whose Hillingdon property is only one asset within a larger portfolio.
Portfolio refinancing often involves interconnected transactions. Equity may be released from one asset to reduce borrowing on another. Several fixed rates may be aligned. Properties may be moved between lenders to improve the overall portfolio structure.
If one Hillingdon HMO cannot complete because its licensing evidence is outstanding, the issue can potentially interfere with a broader refinancing strategy.
That is why the most useful response to the new regime is not to wait until a mortgage is due.
Landlords with smaller shared properties should establish now which assets are affected and place the relevant licensing information alongside their mortgage maturity schedule.
Which Hillingdon properties in the portfolio now require a licence, and do any of those properties have mortgage facilities expiring before the licensing position can comfortably be evidenced to a new lender?
HMO Mortgageability Is Wider Than the Licence
A licence should not be viewed as a guarantee that a property will meet mortgage criteria.
Specialist lenders can consider a wider range of factors including room sizes, communal space, amenities, fire precautions, property configuration, planning, valuation methodology, landlord experience and rental coverage.
The property itself also has to fit the lender's HMO appetite.
That distinction is important because local-authority compliance and mortgage suitability answer different questions. A council licence concerns the regulatory operation of the HMO. A mortgage lender is assessing whether it is willing to take the property as security on the proposed terms.
A landlord should therefore avoid assuming that obtaining the licence automatically solves every finance issue.
A Hillingdon HMO Mortgageability Audit
The most useful action for landlords affected by the new regime is to bring the licensing and mortgage review together.
Rather than waiting until a fixed rate has almost expired, the property can be assessed against the landlord's future financing requirement now.
That review should establish the occupancy, licence position, planning status, current lender, outstanding balance, mortgage expiry and whether the landlord intends to retain, refinance, raise capital or sell.
The proposed lender universe can then be researched against the actual property and licensing circumstances.
Where an issued licence is likely to be required before completion, the mortgage timetable can be planned around it rather than discovering the requirement after valuation or legal work has already started.
The Introducer Opportunity Is Equally Important
Hillingdon letting agents, landlord accountants, HMO managers, licensing consultants, solicitors and planning advisers are likely to encounter affected landlords before mortgage brokers do.
A letting agent may know immediately which properties contain three unrelated professional tenants. An accountant may know that a landlord intends to refinance several assets this year. A licensing consultant may discover that the client has an expensive bridge approaching maturity.
That creates a useful point of professional coordination.
Willow does not need to advise on whether the property satisfies Hillingdon's licensing or planning requirements. The relevant specialists can deal with those matters while Willow establishes what the position means for the mortgage.
For advisers working with Hillingdon landlords, the key question is:
“If your client's property now needs an HMO licence, has anyone checked whether that changes their next remortgage?”
How Willow Private Finance Can Help
Willow Private Finance works with professional landlords, HMO investors, limited companies and portfolio borrowers across specialist buy-to-let and more complex property finance.
For a Hillingdon landlord affected by the additional licensing regime, our role is to establish how the property's current regulatory position interacts with the available mortgage market.
That can include reviewing refinance options, capital raising, SPV borrowing, portfolio restructuring and specialist HMO lenders, while identifying any lender requirements that need to be satisfied before valuation, offer or completion.
Licensing and planning advice should remain with Hillingdon Council and the landlord's appropriate legal, planning or licensing advisers.
The finance question is narrower but potentially time-sensitive: is the property ready for the mortgage transaction the landlord intends to complete?
Own a HMO or Shared Buy-to-Let Property?
If you are refinancing an HMO, raising capital or restructuring a landlord portfolio, Willow can assess the specialist buy-to-let market against the property's actual occupancy, licensing and ownership position. For Hillingdon landlords, checking those requirements before the mortgage approaches maturity can prevent a regulatory issue becoming a completion problem.
Explore Buy-to-Let MortgagesFrequently Asked Questions
Hillingdon's additional licensing scheme changes the position for many smaller shared properties. These are some of the key questions for landlords considering a mortgage or refinance.
Which HMOs now need an additional licence in Hillingdon?
Hillingdon's borough-wide additional licensing designation applies to HMOs occupied by three or more people forming two or more households where the property is not already covered by mandatory HMO licensing, subject to the statutory exclusions. This means qualifying three- and four-person shared properties can now require a licence.
Can an HMO licence affect a mortgage or remortgage?
Yes. Lender requirements vary, but HMO licensing and planning can form part of mortgage underwriting and conveyancing. Some specialist lenders require an issued local-authority HMO licence before they will release refinance funds, so the licensing position should be checked before committing to a completion timetable.
Is applying for an HMO licence enough to complete a remortgage?
Not necessarily. It depends on the proposed lender's criteria. Evidence that an application has been submitted and an issued licence are not automatically treated as equivalent. Where the lender requires the final licence before completion, the council's processing timetable can become relevant to the refinance.
Does an HMO licence also provide planning permission in Hillingdon?
No. Licensing and planning are separate. Hillingdon also operates a borough-wide Article 4 Direction affecting conversion from a Class C3 dwellinghouse to a Class C4 HMO. Landlords should therefore establish the property's planning position separately and obtain specialist planning or legal advice where necessary.
What should a Hillingdon landlord check before refinancing an HMO?
The starting point should include the number of occupiers and households, licensing status, identity of the licence holder, planning position, tenancy structure, property standards, existing mortgage maturity and the proposed lender's licensing requirements. Reviewing these matters early can reduce the risk of discovering a completion condition late in the transaction.