Section 24 & BTL Tax Planning
Section 24 mortgage interest restriction is the biggest single change to BTL taxation in a decade. For higher-rate landlords with substantial finance costs, the personal-name holding model is materially worse than incorporation in many portfolios. Specialist accountants model your Section 24 exposure exactly, assess whether incorporation into a SPV is justified at portfolio scale, and advise on the structural choices (Form 17, partnership, joint ownership) that move the after-tax position.
What Section 24 & BTL Planning Actually Involves
Since April 2020, individual landlords can no longer deduct mortgage interest from rental income. Instead, finance costs receive a 20% basic-rate tax credit. For higher-rate (40%) and additional-rate (45%) landlords with substantial finance costs, this can mean materially more tax than the rental cash flow suggests — sometimes 60%+ effective rate on the rental income after allowing for the credit. Specialist accountants model the Section 24 effect explicitly each year and advise on incorporation timing where the after-tax position justifies it.
The Section 24 calculation: total rental profit (rental income minus allowable expenses, where expenses now exclude mortgage interest) is taxed at your marginal rate. Then a 20% basic-rate tax credit on finance costs is given against the SA tax bill. Specialist accountants get the calculation right and identify carry-forward credits where finance costs exceed available tax in a year (the unused credit carries forward indefinitely, but generalist accountants frequently miss the carry-forward across years and lose the relief).
The Section 24 restriction applies to mortgage interest specifically — not to all finance costs. Arrangement fees, broker fees, valuation fees, product-switch fees, and other ancillary finance costs remain fully deductible as revenue expenses. Generalist accountants frequently apply the 20% restriction to all finance costs (overstating tax); specialist accountants split the components correctly.
Incorporation into a SPV is the standard response for higher-rate-tax landlords with substantial finance costs and 5+ year hold horizons. Inside a limited company, mortgage interest is fully deductible from corporation tax (no Section 24 restriction). The breakeven calculation involves SDLT cost on incorporation (typically £80-130k on a £1.5m portfolio), CGT on personal-side disposal, ongoing corporation tax at 19-25% + dividend tax versus personal income tax with Section 24. Specialist Harrow accountants model this each year for clients above the higher-rate threshold; generalist accountants frequently default to "incorporate" without modelling the SDLT properly.
Form 17 declaration to split BTL income unequally between spouses is a powerful pre-incorporation lever. Married couples and civil partners default to a 50/50 income split for tax purposes regardless of legal beneficial ownership, unless Form 17 is filed declaring an unequal split that matches the legal beneficial ownership exactly. Restructuring to a 70/30 or 80/20 split toward a basic-rate-tax spouse can save £3-8k/year of tax with a one-off legal cost (Deed of Trust + Form 17 filing) of ~£500-£800. Specialist accountants identify Form 17 opportunities; generalists frequently leave the 50/50 default in place even where a split would save material tax.
Where Section 24 & BTL Planning Catches Landlords Out
Pre-letting refurbishment confused with revenue — costs incurred before the first tenant moves in are NOT current-year revenue expenses. Pre-letting refurb is capital, added to the property base cost for eventual CGT. Generalist accountants frequently treat pre-letting refurb as immediate revenue, which is wrong and creates HMRC enquiry exposure on review.
Capital expenditure split — improvements creating a new asset or upgrading beyond original specification are capital (added to base cost), not current-year revenue. Like-for-like replacements are revenue. The boundary catches landlords out: a like-for-like boiler replacement is revenue, an upgrade to a higher-spec system is capital. Specialist accountants apply the test correctly; generalists default to expensing everything (the easier short-term answer that creates long-term exposure).
Replacement of domestic items relief — replaces wear-and-tear allowance from 2016. Allows deduction for replacing furniture, appliances, kitchenware (but NOT initial purchase, NOT improvements). Like-for-like replacement is fully revenue; an upgrade to better-spec items is partial revenue (the like-for-like portion only) plus capital (the upgrade portion).
Furnished holiday letting (FHL) — properties meeting specific criteria (UK-located, fully furnished, available 210+ days, actually let 105+ days, no single letting exceeding 31 days for at least 7 months) qualify for FHL treatment with materially better tax rules: full mortgage interest deduction (no Section 24), capital allowances available, business asset disposal relief on sale. The FHL regime is being phased out from April 2025 — specialist accountants navigate the transition planning for current FHL operators.
Section 24 carry-forward losses — finance costs that exceed the 20% credit available in a year (because there's insufficient tax liability to absorb the credit) carry forward indefinitely against future credits. The carry-forward calculation is multi-year and frequently miscalculated by generalists who don't track it across years.
Joint ownership between unrelated parties versus spouses — partnership tax rules apply to joint ownership between unrelated parties, with income split per the partnership agreement. Spouse joint ownership defaults to 50/50 unless Form 17 declares otherwise. The two regimes are different and shouldn't be conflated.
How Section 24 Planning Plays Out
Section 24 calculation rebuild for higher-rate landlord
Higher-rate-tax Harrow landlord with 3 BTL properties had been calculating Section 24 incorrectly — applying the restriction to all finance costs (£8,400/year of arrangement fees, broker fees, valuation fees, plus £21,200 of mortgage interest). Correct treatment: Section 24 applies to the £21,200 of mortgage interest only; the £8,400 of other finance costs is fully deductible. Recalculated 3 years of returns; net tax recovery £2,600 across the period plus a clean baseline going forward. Set up the carry-forward tracker so unused 20% credit isn't lost in years where rental profit is insufficient.
Form 17 restructure, married couple BTL portfolio
Married couple holding 4-property BTL portfolio with one spouse on additional rate (45% bracket) and the other a basic-rate-only earner. Default 50/50 income split was costing ~£5,800/year extra tax versus an 80/20 split with the basic-rate spouse holding the larger share. Restructured legal beneficial ownership to 80/20 via Deed of Trust, filed Form 17 declaration with HMRC, applied the 80/20 split going forward. Annual saving ~£5,800; one-off legal cost £680 amortised over 1.5 months.
SPV incorporation modelling, 5-property Harrow landlord
Higher-rate-tax landlord with 5 BTL properties (mix of HMO and standard BTL) generating £180k gross rents and ~£68k mortgage interest. Section 24 in personal hands cost ~£11k/year of additional tax versus pre-2017 full-deduction treatment. Modelled SPV incorporation: SDLT on the £1.85m portfolio (after Multiple Dwellings Relief) ~£82k, CGT on personal-side disposal ~£28k, ongoing corporation tax savings vs personal income tax ~£18k/year. Net of one-off costs, breakeven at year 6.5 with cumulative savings thereafter. Recommended phased incorporation aligned with refinance windows; modelled the year-by-year position to validate the call.
Section 24 & BTL planning across the Harrow catchment
Section 24 work runs across all the Harrow-area portfolios. Each location has its own profile:
Section 24 & BTL planning in Harrow
Section 24 & BTL planning in Pinner
Section 24 & BTL planning in Ruislip
Section 24 & BTL planning in Edgware
FAQs on section 24 & btl planning
How does Section 24 affect me as a higher-rate-tax landlord?
When does Section 24 make incorporation worthwhile?
Can I use Form 17 to split BTL income with my spouse unequally?
What's the difference between revenue and capital expenditure for my BTL?
Do I have to apply Section 24 to all my finance costs?
What happens if my Section 24 credit can't be used in a year?
Are furnished holiday lets affected by Section 24?
Can I avoid Section 24 by holding through a partnership?
Other property tax specialisms
Inheritance & Lifetime Planning
Inheritance tax planning for Harrow property owners is the dominant work in this network — `lifetime planning harrow`, `inheritance tax planning harrow`, and `estate planning harrow` are all live.
Capital Gains Tax (Property)
Capital Gains Tax on property disposal is decoupled from main self-assessment by the 60-day reporting requirement (since April 2020 for UK-resident landlords, since 2015 for non-residents).
SPV & Property Company Structuring
A property SPV (Special Purpose Vehicle) is a limited company holding buy-to-let or property investment assets.
Stamp Duty Planning
Stamp Duty Land Tax planning matters most where the property purchase has structural complexity — multiple dwellings in a single transaction, mixed-use property, non-residential elements, the 3% additional dwelling surcharge for second-property buyers and SPV purchasers.