Section 24’s long shadow: what a decade of tax reform has really done to rental housing supply

April 2017 marked the beginning of one of the most consequential fiscal shifts in modern private renting. Section 24, the restriction on mortgage interest relief for individual landlords, was phased in over four years. It was presented as a fairness measure. Nearly a decade on, the deeper question is whether it achieved its wider economic purpose.

At the time, the stated objectives were clear. Policymakers argued that highly leveraged landlords were distorting competition, outbidding first-time buyers and benefiting from tax treatment unavailable to homeowners. Restricting finance cost deductibility would, it was said, level the playing field and moderate investor demand.

That was the theory.

What followed was not a uniform retreat from the sector, it was more nuanced. Landlords with significant borrowing saw effective tax rates rise sharply, interest cover ratios tightened, and refinancing became more complex. In some cases, portfolios that appeared profitable before tax became cashflow negative after tax. Behaviour shifted accordingly.

Some deleveraged while others sold selectively. Many explored incorporation, transferring activity into company structures where finance costs remain deductible, a subject frequently debated on Property118 over the past decade. The surge in restructuring conversations was reflected in media commentary. The market adapted, but it did not stand still.

The commercial effects were uneven. Some landlords with low gearing absorbed the change. Those with higher borrowing in regions with slower rental growth felt pressure more acutely. Geography, portfolio scale, and timing mattered.

The supply question, however, is harder to answer and far more important.

If the objective was to expand owner-occupation and moderate investor participation, then the relevant metric is not tax collected. It is housing allocation. Have former rental properties transferred meaningfully into first-time buyer hands? Has total rental stock contracted in specific regions? Have institutional entrants offset any exit by smaller operators? Have rents moved differently in areas with historically higher leverage?

Some data exists, clean conclusions do not.

Incorporation statistics show structural change, yet they do not necessarily reveal whether stock was lost or simply restructured. Rental growth is measurable, but causation is contested. The interaction between fiscal reform, interest rate cycles and demographic demand complicates any simple narrative. Wider reforms, including the evolving Renters’ Reform Bill coverage, have also altered landlord confidence during the same period.

What is clear is that Section 24 altered risk perception. When fiscal treatment changes abruptly, capital responds cautiously. For many landlords, the issue was not ideology but predictability. Business planning depends on stable assumptions, so when those assumptions shift, investment decisions follow.

The international context also adds perspective. Several European jurisdictions retain full finance cost deductibility within their rental sectors. Others impose caps but offset them with capital incentives or longer transition periods. The UK chose a comparatively direct recalibration. Whether that model has produced more stable long-term outcomes remains an open empirical question.

It is also important to disentangle policy from macroeconomics. Interest rates rose sharply after Section 24 was implemented. Pandemic distortions followed. Inflationary pressures compounded operating costs. Untangling the specific impact of tax reform from wider economic cycles requires longitudinal analysis rather than short-term commentary.

Nearly ten years on, the debate should move beyond fairness narratives towards measurable outcomes. If rental supply contracted materially, policymakers need to understand why. If ownership patterns shifted, the evidence should be transparent. If incorporation became the dominant adaptation mechanism, that carries its own financing and regulatory implications.

Section 24 was one of the earliest signals of a broader recalibration of landlord policy. Its long shadow remains visible in refinancing behaviour, portfolio structuring and investment modelling. It also sits within a wider reform landscape that Property118 has documented extensively, including the original Section 24 comprehensive report that examined anticipated commercial consequences at the time of implementation.

Now there is enough distance to assess outcomes with greater clarity.

Expanding the Property118 housing research panel

Property118 has recently launched its Housing Research Panel to examine long-term policy impacts across multiple housing markets. The objective is not to relitigate old arguments; it is to test outcomes against intent.

If Section 24 reshaped the private rented sector, we should be able to measure how. If it did not, that deserves equal scrutiny.

The next phase of housing reform will be more credible if it is grounded in evidence rather than assumption. Landlords who wish to contribute data, comparative insight or independent analysis are encouraged to join the Property118 Housing Research Panel and take part in shaping a more rigorous evaluation of modern housing policy.

We are also inviting the following to contribute to and utlise our research by contacting [email protected]:

• Journalists with access to regional rental supply data

• Economists analysing housing allocation trends

• Academics studying the relationship between fiscal reform and housing elasticity

Tax policy rarely ends where it begins; it flows through refinancing decisions, supply pipelines, rent negotiations and household formation.

A decade provides sufficient distance for reflection; the evidence now needs to follow.