Is Stamp Duty deductible from capital gains?

Yes. SDLT paid when buying is an allowable acquisition cost.

Can I deduct a new boiler?

Usually not — replacing a boiler is a repair. Installing central heating where none existed can be an improvement.

Are mortgage costs allowable?

No. Interest and loan arrangement fees are not allowable for CGT.

Allowable costs for property CGT

TCGA 1992 s.38 allows three categories of expenditure: acquisition costs, enhancement costs reflected in the property at sale, and disposal costs.

Updated for the 2026/27 tax year · Reviewed against HMRC guidance

What you can deduct

Category	Allowable	Not allowable
Buying	SDLT/LBTT, conveyancing, survey, search fees	Mortgage arrangement fees
Improving	Extensions, loft conversions, new kitchen replacing none, conservatory	Repairs, redecoration, like-for-like replacements
Selling	Estate agent, conveyancing, EPC, advertising	Removal costs

Improvements must still exist

Enhancement expenditure is only deductible if it is reflected in the state of the asset at the time of sale. A conservatory you later demolished doesn't count.

Keep evidence

Keep invoices and completion statements. HMRC can ask for evidence of costs claimed for up to several years after the return.

Frequently asked questions

This guide is general information based on the Taxation of Chargeable Gains Act 1992 and HMRC guidance (including HS283). It is not personal tax advice — for complex cases speak to a qualified tax adviser.