There's a common misconception among basic rate taxpayers that Section 24 — the mortgage interest restriction — doesn't affect them. The thinking goes: "I'm only paying 20% tax anyway, so the 20% tax credit balances out."

This assumption can be costly. Section 24 affects basic rate taxpayers in ways that aren't immediately obvious, potentially pushing you into higher tax brackets and reducing your actual take-home income from property.

How Section 24 Works for Basic Rate Taxpayers

Before Section 24, you could deduct mortgage interest as a business expense. Now, you add the interest back to your taxable income, then claim a 20% tax credit against your final tax bill.

For basic rate taxpayers, this creates several problems:

  • Income bracket creep: Adding back mortgage interest can push you over the higher rate threshold (£50,270 for 2025/26)
  • Benefit restrictions: Higher reported income can affect child benefit and other means-tested support
  • Cash flow impact: You pay more tax upfront and get the relief later
  • Student loan implications: Higher income triggers larger student loan repayments

Real Example: Basic Rate Taxpayer Impact

Consider Sarah, who earns £35,000 from her day job and has two BTL properties generating £18,000 rental income. Her annual mortgage interest is £12,000.

Before Section 24:

  • Employment income: £35,000
  • Rental profit (£18,000 - £12,000): £6,000
  • Total taxable income: £41,000
  • Tax rate: 20% basic rate

After Section 24:

  • Employment income: £35,000
  • Rental income: £18,000 (no mortgage deduction)
  • Total taxable income: £53,000
  • Tax: 20% on £50,270 + 40% on £2,730
  • Less 20% credit on £12,000 mortgage interest

Sarah now pays higher rate tax on £2,730 and loses child benefit if she has children. Her effective tax rate on the property income increases significantly.

The Hidden Costs Beyond Tax Rates

The impact goes beyond just tax calculations. Many basic rate taxpayers discover they're affected by:

Child Benefit Clawback: If your adjusted net income exceeds £50,000, you start losing child benefit. The mortgage interest addition can trigger this unexpectedly.

Student Loan Repayments: Plan 2 student loans require 9% repayments on income over £27,295. Adding back mortgage interest increases your repayable income.

Personal Allowance Tapering: While this starts at £100,000, landlords with multiple properties can find themselves closer to this threshold than expected.

When Basic Rate Taxpayers Are Most at Risk

You're particularly vulnerable to Section 24 impact if:

  • Your total income is between £40,000-£60,000
  • You have high mortgage interest relative to rental income
  • You receive child benefit or other income-tested benefits
  • You're still paying student loans
  • You have other income sources that fluctuate

Even landlords with just one or two properties can find themselves caught out, especially in areas where property values (and therefore mortgage amounts) are high relative to rental yields.

What You Can Do About It

If you're a basic rate taxpayer affected by Section 24, you have several options:

Consider Incorporation: Moving your properties into a limited company can restore full mortgage interest deductibility. However, this involves other costs and complications that need careful analysis.

Reduce Other Income: If possible, consider timing bonuses, dividend payments, or pension contributions to manage your total income level.

Review Your Portfolio: High-yield, low-mortgage properties are less affected by Section 24 than highly leveraged investments.

Get Professional Advice: The interaction between Section 24 and other parts of the tax system is complex. Our specialist property tax services can help you understand your specific situation and explore options like property company incorporation.

Planning for 2025/26 and Beyond

With Making Tax Digital for Income Tax Property starting in April 2026, now is a good time to review your property tax position. The quarterly reporting requirements will make these Section 24 impacts more visible throughout the year.

Use our tax calculators to model different scenarios and understand how Section 24 might affect your specific situation. Remember that tax planning works best when done proactively rather than reactively.

Don't assume that being a basic rate taxpayer protects you from Section 24's impact. The mortgage interest restriction can affect your finances in unexpected ways, even if your marginal tax rate appears unchanged.