Section 24 Tax Impact Calculator

Written by Scott Jones, founder of PropertyKiln.

See exactly how much extra tax Section 24 costs you on your BTL portfolio — at every tax band.

This calculator provides estimates based on current UK tax rates and regulations. It is not financial advice. Results depend on your individual circumstances. Consult a qualified accountant for advice specific to your situation.

Annual rental income (£)

Annual mortgage interest paid (£)

Interest only — not capital repayments.

Other allowable expenses (£)

Letting agent fees, repairs, insurance, ground rent, etc.

Other (non-property) income (£)

Salary, dividends, pensions — used to confirm your tax band.

Your highest tax band

Basic rate (20%) Higher rate (40%) Additional rate (45%)

Uses 2025-26 tax rates. Section 24 restricts mortgage interest relief on individually-held BTL to a 20% basic-rate tax credit.

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