Rent Caps With Tax Relief Restored Would Cut Rents £1,200: Why This Proposal Is More Dangerous Than It Appears

A policy proposal circulating in housing research circles has attracted renewed attention this week: restore mortgage interest tax relief for private landlords, but attach a rent cap as the political price. The headline figure being cited is a potential reduction of £1,200 per year in average rents. To some landlords, that framing might sound like a straightforward exchange, give up Section 24, get it back, accept a ceiling in return. The reality is considerably more complicated, and landlords who read this as a neutral trade are misreading the structural consequences.

Section 24 of the Finance Act 2015, which phased out mortgage interest relief and replaced it with a 20 per cent tax credit, remains the single most consequential tax change the private rented sector has experienced in a generation. For higher and additional rate taxpayers, the reform did not merely reduce profit margins; it restructured the entire basis on which leveraged portfolios generate taxable income. Landlords with significant mortgage debt found themselves taxed on revenue rather than profit, in some cases producing tax bills that exceeded the actual cash yield on a property. The political logic behind restoration is straightforward: reverse an acknowledged distortion, reduce upward pressure on rents, demonstrate good faith to a sector that has been systematically squeezed since 2015. The economic logic is less clean.

Does Restoring Tax Relief Actually Produce Lower Rents, or Does It Simply Restore Viability?

The £1,200 figure deserves scrutiny before it becomes the anchor around which any debate is framed. It appears to derive from modelling that assumes restored relief would reduce landlord cost pressure sufficiently to suppress rent increases, or in some markets to prompt modest reductions. That assumption treats rents as a direct function of landlord costs, which is only partially accurate. In supply-constrained markets, and the majority of high-demand English cities qualify as supply-constrained, rents are set by competition among tenants rather than by landlord cost calculations. A landlord in Manchester or Bristol does not price below market rate because their mortgage costs have fallen; they price at what the market will bear, because another landlord will if they do not.

The £1,200 estimate is therefore more credible as a description of what landlords in lower-demand markets might pass through to tenants, where vacancy risk incentivises competitive pricing, than as a national average with predictive reliability. Treating it as the latter is a political convenience, not an analytical conclusion. What restoration would more reliably produce is improved viability for leveraged landlords in marginal markets, some re-entry of landlords who exited after 2015, modest supply recovery over three to five years, and consequently some downward pressure on rents through volume rather than through direct cost pass-through. That is a legitimate argument for restoration. It is a slower and less direct mechanism than the £1,200 headline implies.

The rent cap component introduces a different order of problem. Any administered ceiling, whether set at inflation, a fixed percentage uplift, or indexed to local wage growth, converts a dynamic market signal into a regulatory floor. Landlords operating with restored tax relief in a capped environment would face reduced incentive to invest in property improvement above the minimum required for compliance, because the mechanism for capturing improved rental value through higher rents would be legally constrained. The combination of restored relief and a cap does not simply balance itself out; it creates a two-tier market in which compliant landlords accept constrained returns while the unregulated short-let and informal sectors absorb unmet demand at uncapped prices.

What Would a Cap Mechanism Actually Look Like, and Which Landlord Structures Are Most Exposed?

No formal legislative proposal with precise cap mechanics has been published. What has been floated is a framework concept: relief restoration as the carrot, a cap as the statutory constraint that makes restoration politically defensible to a government wary of being seen to hand income tax advantages back to property investors. The details matter enormously, and landlords should not assume that any cap would be designed with their operational realities in mind.

If a cap were set at Consumer Price Index plus one or two percentage points, it would bind most tightly in precisely the markets where rent growth has been fastest: London, the South East, and major university cities. A landlord with a portfolio acquired between 2012 and 2018 at lower prices and refinanced at today's rates has a cost structure that in many cases already requires above-inflation rent increases simply to remain cash-flow neutral. A statutory cap in that environment does not stabilise the market; it accelerates exit decisions among exactly the landlords whose properties are most likely to be well-maintained and professionally managed.

Limited company structures, which have become the dominant vehicle for new landlord investment since Section 24 made personal ownership less tax-efficient, would face a different but related exposure. Corporate landlords operating through special purpose vehicles already manage rental income at corporation tax rates with full mortgage interest deductibility. Restoration of personal relief narrows the tax efficiency gap between personal and corporate ownership, potentially reducing the incentive to incorporate further. A rent cap applied universally, including to corporate vehicles, would constrain revenue growth regardless of structure. Portfolio landlords who incorporated specifically to escape the Section 24 regime would find that the restoration they were denied as individuals arrives simultaneously with a new constraint on the revenue side.

The interaction with the Renters' Rights Act provisions, which are still being absorbed across the sector, adds a further layer of complexity. Periodic tenancies without fixed terms, combined with a rent cap mechanism that limits in-tenancy increases, would reduce the landlord's ability to align rents with market rates over the tenancy lifecycle. The practical consequence is that the gap between sitting-tenant rents and market rents, already a feature of longer tenancies, would widen structurally. Landlords would face pressure to price new tenancies as aggressively as the cap allows from day one, precisely because subsequent adjustment would be constrained. That is not a behaviour pattern that produces lower rents in aggregate.

How Should Landlords Position Themselves Before This Enters the Legislative Pipeline?

This proposal has not been introduced as a Bill. It exists as a policy idea with a compelling headline number attached to it, and that is precisely when landlords need to engage rather than wait. The political conditions for something like this to advance are not implausible: a government under sustained pressure on housing affordability, a Treasury looking for revenue-neutral interventions, and a landlord sector that has spent a decade being characterised as the obstacle to affordable housing rather than part of its solution. The restoration-plus-cap framing allows ministers to claim they have responded to landlord hardship while simultaneously capping the benefit to tenants. It is tidy politics.

Landlords with mortgaged portfolios in their personal names should model the restoration scenario now, not to celebrate it, but to understand what their actual tax position would be at different cap levels. A landlord currently managing around the Section 24 constraint through a combination of accelerated overpayment, corporate restructuring, or selective disposal needs to know whether partial restoration changes the calculus before acting on existing plans. Restructuring decisions made in the next twelve months may be overtaken by a policy environment that looks different by 2027.

The broader point is that this proposal is not primarily a tax story. It is a market structure story dressed in tax clothing. Restored relief changes landlord incentives at the margin. A rent cap changes the fundamental economics of holding leveraged residential property as an income asset. Landlords who evaluate it only through the tax lens will miss the more durable consequence, which is what a capped, regulated, periodic-tenancy market does to the long-term return profile of property investment in the United Kingdom.