A landlord who replaces a boiler in a let home has two tax questions: whether the cost can be deducted against rental income, and whether it counts as a repair or a capital improvement. HMRC’s Property Income Manual and Business Income Manual set out how it approaches those questions. This guide summarises that guidance as it stood in September 2026 for income tax and corporation tax on property businesses. It is general information about HMRC’s published view, not tax advice.

A boiler is a fixture, not a domestic item

PIM3210 explains “replacement of domestic items relief”, which allows a deduction for replacing certain items in a let dwelling. HMRC says domestic items are things such as moveable furniture, furnishings, household appliances and kitchenware. It says fixtures are not domestic items and do not qualify, and it defines fixtures to include any boiler or water-filled radiator installed in a dwelling-house as part of a space or water heating system, alongside baths, washbasins and toilets.

PIM3210 adds that, because these items are fixtures of the building, the cost of replacing them may be an allowable expense as a repair to the building. It warns that expenditure is not on repairs if an “entirety” is replaced.

Repair or capital: the entirety

BIM46910 says the cost of repairing a worn or dilapidated asset is normally an allowable expense, while the cost of replacing the whole or the “entirety” of an asset is capital expenditure and not allowable. Whether something is a separate asset is a question of fact and degree, and there are no fixed tests. The same page says that if something is a fixture it has become part of the building and is not an entirety in its own right, and that, except where an integral feature is being replaced, replacing a fixture is a repair to the building.

Same job as before, or something better

The other test is whether the work restores or improves. BIM46915 says that if the taxpayer restores an asset to what it originally had been, the expenditure is normally allowable, but if the asset is altered or improved it is not a repair and the expenditure is capital. BIM46920 puts the test as whether, after the work, the asset can just do the same job as before, in which case the work is a repair, or whether more can be done with it or it can do something it could not do before, in which case it is an improvement. Trivial increases in performance or capacity arising solely from newer but broadly equivalent materials are still a repair, according to PIM2030.

BIM46925 covers changing technology. It says that using new technology as part of a repair does not necessarily make it an improvement, and that what counts as an improvement can change over time as a technology becomes the industry standard. Its example is double glazing, which HMRC says ceased to be an improvement once it became the norm. Whether a given replacement is like for like is a question of fact and degree.

When repairs and improvements are bundled

PIM2030 says work commissioned on a property may include capital works and separate repairs at the same time. Expenditure on the repairs remains allowable, and the total can be apportioned on a reasonable basis. A split shown in the contractor’s bill may be a sensible basis, but it must be done fairly and can be reviewed if capital expenditure is wrongly described as repairs. If the work is an alteration or improvement, BIM46915 says no revenue deduction is available for any part of it, including redecoration after the main work, and no deduction is available for the notional cost of simply repairing the old asset. An installer’s itemised quote and invoice therefore matter, (see comparing installation quotes).

A boiler replaced soon after buying the property

PIM2030 says repairs to reinstate a worn asset are usually deductible, and that buying the asset not long before the repair does not by itself make the repair capital. A change of ownership combined with other factors can make it capital, for example where the property was not fit for use in the business until the repairs were carried out, or where the price paid was substantially reduced because of the dilapidated state. The guide to buying a home with an older boiler covers what to check at purchase.

Integral features and the accountant

BIM46945 lists a space or water heating system among the “integral features” for which special capital allowances rules apply, including a rule about spending that represents more than half the cost of replacing the feature. PIM2030 also states that there are no capital allowances for the cost or depreciation of residential property. The accountant can confirm which rules apply to a particular property. The landlord’s separate safety duties are covered in the guide to landlord gas safety certificates.

FAQs

Does replacement of domestic items relief cover a boiler?

No. PIM3210 says fixtures are not domestic items and defines fixtures to include a boiler installed as part of a space or water heating system.

Is replacing a boiler with a more efficient model an improvement?

It depends on the facts. BIM46920 asks whether the asset can only do the same job as before, and BIM46925 says new technology does not automatically make a repair an improvement.

Can a landlord split one invoice into repair and improvement?

PIM2030 allows apportionment on a reasonable basis where repairs and capital works are done together, and warns that the figures may be reviewed.

The bottom line

HMRC treats a boiler as a fixture, so replacing it can be a repair to the building if the new boiler does the same job as the old one, but replacing an entirety or making an improvement is capital expenditure and not deductible against rental profits. Mixed jobs can be apportioned on a reasonable basis. This is general information, not tax or regulated advice on any specific installation.

Sources

This guide draws on the following primary sources, current as of 25 September 2026:

• HMRC, “Property Income Manual PIM3210: Furnished lettings: Replacement of domestic items relief: 2016-17 onwards”
• HMRC, “Property Income Manual PIM2030: Deductions: repairs: is it capital?”
• HMRC, “Business Income Manual BIM46910: Repairs and renewals: what is a repair: the entirety”
• HMRC, “Business Income Manual BIM46920: Repairs and renewals: what is a repair: different materials”
• HMRC, “Business Income Manual BIM46925: Repairs and renewals: what is a repair: changing technology”
• HMRC, “Business Income Manual BIM46945: Repairs and renewals: assets on which capital allowances given”

Related guides

Best Boiler Deals is an independent guide. We may earn a fee from some links; this never affects what we write. This article is general information, not regulated advice on any specific installation — always confirm the details with a Gas Safe registered engineer.