The short answer
Repaying the capital on a mortgage isn't an expense and gets no relief. Only the interest and finance costs count, in box 44.
It's not a cost of the business at all: it repays money you borrowed.
What you can and can't claim
| You can claim | You can't claim |
|---|---|
| Interest on the mortgage (box 44, basic-rate credit) | The capital part of repayment-mortgage payments |
| Arrangement fees (box 44) | Overpayments to reduce the loan |
Worked example
Monthly payments are £900, of which £400 is interest and £500 capital. Over a year, £4,800 of interest goes in box 44. The £6,000 of capital isn't claimable.
Where it goes on your tax return
Leave it off your return. Only the interest goes in box 44. See can landlords claim mortgage interest?
Repair or improvement: how HMRC decides
A repair restores something to its previous condition, even if modern materials make it a bit better. An improvement adds something new or makes it significantly better, and is capital. Timing also matters from 2027: a cost paid before 6 April 2027 saves tax at 20%/40%/45%, after that at 24%/44%/49%. See all landlord expenses A to Z.
Frequently asked questions
Can I claim my whole mortgage payment as an expense?
No. Only the interest, and only as a basic-rate credit.
Does this mean landlords pay tax on cash they don't have?
Often, yes. Profit can be higher than cash flow because capital repayments aren't deductible.
Sources
- GOV.UK: Work out your rental income when you let property
- HMRC: UK property notes (SA105 Notes 2025)
- HMRC Property Income Manual: repairs, replacements and allowable costs
Sources last checked 10 November 2026. See all our sources and how we keep pages up to date.