Section 24 Mortgage Interest Relief: How It Affects Landlords in 2025/26
How Section 24 restricts mortgage interest relief for UK landlords, how to calculate your tax, and strategies to reduce the impact on your rental profits.
Key Takeaways
- Mortgage interest is no longer deductible from rental income
- You get a 20% tax credit instead (regardless of your tax band)
- Higher-rate taxpayers are hit hardest - effectively losing 20% of previous relief
- Limited company ownership isn’t affected (but has other implications)
Section 24 is the single biggest tax change to hit UK landlords in decades. If you have a mortgage on your rental property, this directly affects how much tax you pay. Here’s exactly how it works and what you can do about it.
What Is Section 24?
Section 24 of the Finance (No. 2) Act 2015 changed how landlords claim relief on mortgage interest and other finance costs.
Before Section 24 (pre-2017):
- Deduct mortgage interest from rental income
- Pay tax on the remaining profit
- Higher-rate taxpayers got 40% relief
After Section 24 (from April 2020):
- Cannot deduct mortgage interest from rental income
- Pay tax on the full rental income
- Receive a 20% tax credit on interest paid
The change was phased in from 2017 to 2020. Since April 2020, the full restriction applies.
How Section 24 Affects Your Tax
Example: Basic-Rate Taxpayer (20%)
| Before Section 24 | After Section 24 | |
|---|---|---|
| Rental income | £15,000 | £15,000 |
| Mortgage interest | £5,000 | £5,000 |
| Taxable profit | £10,000 | £15,000 |
| Tax at 20% | £2,000 | £3,000 |
| Tax credit (20% of £5k) | N/A | -£1,000 |
| Final tax bill | £2,000 | £2,000 |
Impact: None - basic-rate taxpayers break even.
Example: Higher-Rate Taxpayer (40%)
| Before Section 24 | After Section 24 | |
|---|---|---|
| Rental income | £15,000 | £15,000 |
| Mortgage interest | £5,000 | £5,000 |
| Taxable profit | £10,000 | £15,000 |
| Tax at 40% | £4,000 | £6,000 |
| Tax credit (20% of £5k) | N/A | -£1,000 |
| Final tax bill | £4,000 | £5,000 |
Impact: £1,000 more tax per year - that’s £1,000 less profit from your property.
Example: Additional-Rate Taxpayer (45%)
| Before Section 24 | After Section 24 | |
|---|---|---|
| Rental income | £15,000 | £15,000 |
| Mortgage interest | £5,000 | £5,000 |
| Taxable profit | £10,000 | £15,000 |
| Tax at 45% | £4,500 | £6,750 |
| Tax credit (20% of £5k) | N/A | -£1,000 |
| Final tax bill | £4,500 | £5,750 |
Impact: £1,250 more tax per year.
The Hidden Problem: Tax Band Creep
Section 24 can push you into a higher tax band because your “profit” is now higher on paper.
Example:
- Salary: £45,000
- Rental income: £12,000
- Mortgage interest: £8,000
- Old taxable income: £45,000 + £4,000 = £49,000 (basic rate)
- New taxable income: £45,000 + £12,000 = £57,000 (higher rate on £6,730)
Even though your actual cash profit is the same, HMRC now sees £8,000 more income. This can:
- Push you into the 40% band
- Trigger High Income Child Benefit Charge (over £50,000)
- Affect student loan repayments
- Reduce personal allowance (over £100,000)
What Finance Costs Are Affected?
All “finance costs” related to your rental property are restricted:
| Cost | Restricted? |
|---|---|
| Mortgage interest | ✅ Yes |
| Buy-to-let loan interest | ✅ Yes |
| Interest on loans for repairs/improvements | ✅ Yes |
| Mortgage arrangement fees | ✅ Yes |
| Early repayment charges | ✅ Yes |
| Overdraft interest (for property expenses) | ✅ Yes |
How to Calculate Your Section 24 Tax Credit
The calculation for your Self Assessment (SA105) is:
- Report full rental income (no mortgage interest deduction)
- Report mortgage interest separately (Box 25 on SA105)
- HMRC calculates 20% tax credit and applies it to your bill
If your finance costs exceed your rental profit, the excess credit carries forward to future years.
Worked Example
| Item | Amount |
|---|---|
| Total rental income | £24,000 |
| Allowable expenses (not mortgage) | £4,000 |
| Rental profit | £20,000 |
| Mortgage interest paid | £10,000 |
Tax calculation (40% taxpayer):
| Step | Calculation | Amount |
|---|---|---|
| Tax on rental profit | £20,000 × 40% | £8,000 |
| Section 24 tax credit | £10,000 × 20% | -£2,000 |
| Tax due on rental income | £6,000 |
Old system comparison: Tax would have been (£20,000 - £10,000) × 40% = £4,000
Section 24 cost: £2,000 extra per year.
Strategies to Reduce the Impact
1. Transfer to Lower-Earning Spouse
If your spouse/civil partner is a basic-rate taxpayer (or non-earner), transferring some or all ownership to them reduces the Section 24 impact.
- Married couples: Use a Deed of Trust to split income differently from ownership
- Form 17: Submit to HMRC to declare the split
Caution: This may trigger Stamp Duty and has CGT implications. Get professional advice.
2. Incorporate (Limited Company)
Limited companies can still deduct mortgage interest in full. However:
- Transferring existing properties triggers CGT and Stamp Duty
- Mortgage rates are typically higher for companies
- Extracting profits is taxed (dividends/salary)
- More admin and accounting costs
Best for: New purchases, high-income landlords, or those building a portfolio.
Not worth it for: One or two properties with small mortgages.
3. Pay Down the Mortgage
Less mortgage = less interest = less Section 24 impact.
If you have savings earning 4% but paying mortgage interest of 5%, paying down the mortgage:
- Saves you money on interest
- Reduces your taxable “profit” under Section 24
- Improves your cash flow
4. Increase Rent (If Market Allows)
Higher rent increases your actual profit, offsetting the tax hit. But this depends on local market conditions and tenant affordability.
5. Offset with Pension Contributions
Pension contributions extend your basic-rate band. If you’re just over the £50,270 threshold, a pension contribution could drop you back to 20% on your rental income.
6. Claim All Other Allowable Expenses
Make sure you’re claiming everything else you’re entitled to. Many landlords miss:
- Mileage to properties (45p/mile)
- Landlord insurance
- Safety certificates
- Software subscriptions
- Professional memberships (NRLA)
See our complete allowable expenses guide for the full list.
Section 24 and Making Tax Digital
Under MTD for landlords, you’ll submit quarterly updates to HMRC. Your MTD software needs to:
- Track mortgage interest separately from other expenses
- Report it in the correct field (
financialCosts) - Calculate the 20% credit correctly in year-end reports
Portiqo handles this automatically - you enter your mortgage interest, and we categorise it correctly for HMRC submission.
Frequently Asked Questions
Does Section 24 apply to limited companies?
No. If you own properties through a limited company, you can still deduct mortgage interest in full before calculating Corporation Tax.
Does Section 24 apply to holiday lets?
No. Furnished Holiday Lets (FHLs) are treated as a trade and can still deduct mortgage interest fully. However, the FHL tax advantages are being removed from April 2025.
Can I still claim mortgage interest if I’m a basic-rate taxpayer?
Yes, and you break even - the 20% tax credit equals what you would have saved anyway. Section 24 only costs you money if you’re a higher or additional-rate taxpayer.
What if my mortgage interest is more than my rental profit?
The excess tax credit carries forward to future years. You won’t get a refund, but you can use it against future rental profits.
Does remortgaging count as finance costs?
Arrangement fees and interest on the new mortgage count. Any cash you release and don’t use for the property is not claimable.
How Portiqo Helps
Section 24 makes landlord tax more complicated. Portiqo simplifies it:
- Automatic categorisation - mortgage interest tracked separately
- Section 24 calculator - see the real impact on your tax bill
- MTD-ready - submits to HMRC with finance costs in the correct field
- Year-end reports - aligned with SA105 boxes
Stop overpaying tax or stressing about calculations. Join the waitlist and get your rental finances sorted before April 2026.
Questions about Section 24? Get in touch or read our allowable expenses guide for other deductions you might be missing.