7 Expense Mistakes That Cost UK Landlords Money

UK landlords collectively miss millions in allowable deductions every year — and some accidentally claim expenses they shouldn't. Both mistakes cost you money. Here are the seven most common errors.

1. Not claiming travel expenses

Journeys to your rental property for management purposes (inspections, meeting contractors, collecting keys) are allowable. You can claim 45p/mile for the first 10,000 miles per tax year. Many landlords forget to track these — keep a simple mileage log or use Tendmere to record visits.

2. Confusing repairs with improvements

This is the most common and costly mistake. Repairs (restoring something to its original condition) are allowable revenue expenses. Improvements (upgrading beyond the original) are capital expenditure — not deductible from income, but potentially deductible against CGT when you sell.

• Allowable: Replacing a broken boiler with a like-for-like model
• Not allowable: Replacing a standard boiler with a high-end combi system with smart controls
• Grey area: HMRC accepts "modern equivalent" replacements — a new double-glazed window replacing an old single-glazed one is generally a repair

3. Forgetting to claim the Replacement Domestic Items Relief

If you let a furnished property, you can claim the cost of replacing domestic items: furniture, appliances, kitchenware, and soft furnishings. You can't claim the initial cost (that's capital), but replacements are deductible. Many landlords miss this entirely.

4. Not separating personal and rental expenses

Using a personal bank account for rental income and expenses makes it easy to miss deductions and hard to prove claims to HMRC. Use a dedicated bank account (even a free one) for all rental transactions.

5. Over-claiming mortgage interest

Individual landlords can only claim a 20% tax credit on mortgage interest — not a full deduction. Some landlords still enter the full interest amount as an expense, which HMRC's systems will flag. Use SA105 box 44 for the tax credit, not box 26 (finance costs).

6. Missing the letting agent fee deduction

All letting agent fees (management fees, tenant-find fees, inventory fees) are allowable expenses. If your agent deducts their fee before paying you, remember to declare the gross rent as income and the agent fee as an expense — otherwise you're under-declaring income and missing the deduction.

7. Not keeping receipts

HMRC can ask to see evidence for expense claims. Use Tendmere's document vault to store receipts as you go. Where assisted extraction is enabled, it proposes amounts and dates for human review rather than filing them automatically.