Is lease extension
tax deductible?

No. The premium and legal costs of extending the lease on a leasehold property you own are capital, not a running cost of letting it (SA105 notes). They are relieved when you sell, as part of the property's cost for Capital Gains Tax. Legal fees for renewing a lease of under 50 years that you grant to a tenant are different, and allowable (GOV.UK).

Many buy-to-let flats are leasehold, and as the lease shortens, the flat loses value and becomes harder to mortgage. Extending the lease restores that value, which is why the cost is capital: it improves what you own. The premium, the valuation and the legal fees are all part of the property's cost, not an expense of letting it.

Is lease extension tax deductible?

The HMRC rule

The cost of buying property, and improvements or enhancements to it, are capital. They are not deducted from rental or trading income, though many count towards the cost for Capital Gains Tax. The rule comes from Work out your rental income when you let property.

The SA105 notes say you can claim legal and professional fees for renewing a lease if the lease is for less than 50 years, but not the costs for agreeing and paying a premium on renewal of a lease (SA105 notes). GOV.UK lists legal fees for lets of a year or less, or for renewing a lease for less than 50 years, as allowable (landlords). Capital costs that increase the value of the property are relieved in the Capital Gains Tax computation (Capital Gains Tax on property).

When you can claim it

• Include the lease extension premium in the property’s cost for Capital Gains Tax.
• Include your legal and valuation fees for the extension in that cost.
• Deduct legal fees for renewing a lease of under 50 years that you grant to a tenant.
• Deduct ground rent and service charges as running costs.

When you cannot

• Deduct the premium paid to the freeholder from rental income.
• Deduct legal and valuation fees for extending your own lease.
• Deduct the freeholder’s costs you are required to pay.
• Deduct the costs of agreeing a premium on any lease renewal.

What to claim instead

Keep the lease extension documents and invoices with the flat's purchase records. When you sell, they are added to the cost, reducing the taxable gain. If you are buying the freehold jointly with other leaseholders, the same capital treatment applies.

How to decide if you can claim it

1. Was it for the business? A cost is only allowable if you incur it wholly and exclusively for the business. If it also serves a personal purpose that cannot be separated, such as clothing that keeps you warm or a meal that keeps you going, HMRC disallows it.
2. Is part of it personal? Where a cost has a business part you can identify, such as the business calls on a phone bill or the business miles in a car, you claim that part and leave the rest out, on a reasonable basis you can explain.
3. Is it a running cost or something you keep? It is something you buy to keep. On traditional accounting that means capital allowances, where the item qualifies, rather than an expense. On the cash basis most equipment is an ordinary expense, but cars, land and buildings never are.
4. Is there a specific rule? For lease extension, the deciding rule is buying and improving property: the cost of buying property, and improvements or enhancements to it, are capital. They are not deducted from rental or trading income, though many count towards the cost for Capital Gains Tax.

Worked example: extending a buy-to-let lease

A landlord's flat has 72 years left on its lease. She pays the freeholder a £14,000 premium to extend it, £1,800 in legal fees, £900 for a valuation and £1,500 towards the freeholder's costs. None of the £18,200 reduces her rental profit, but all of it is added to her cost when she sells.

Why a lease extension is capital

A lease extension gives you a longer interest in the property, which lasts for decades and increases its value. That is the classic sign of capital expenditure. It is not maintaining the letting business; it is improving the asset you let.

Renewing leases you grant

If you let commercial property on leases, the legal fees for renewing a lease of under 50 years to your tenant are allowable, because they maintain the letting. The cost of the first grant of a lease of more than a year is not. This is a different situation from extending your own lease.

Buying the freehold

Joining other leaseholders to buy the freehold of a building is also capital. Your share of the price and costs is added to your cost for Capital Gains Tax. Ongoing costs of running the freehold company, if you use one, follow their own rules.

Ground rent and service charges

The ground rent and service charges you pay as a leaseholder are running costs of letting the flat, allowable in box 24 of the UK property pages. A lease extension often reduces ground rent to a peppercorn, which lowers these costs in future.

Capital Gains Tax on sale

When you sell, the gain is the sale price less the purchase price, buying and selling costs, and capital improvement costs, including the lease extension premium and fees. Residential property gains are reported and paid within 60 days of completion.

Your own home

If the flat is your main home, the extension is personal and any gain on sale is usually covered by private residence relief. Keep the records anyway, in case you let the flat later.

If you are a landlord

Lease extension premiums and fees for a leasehold property you let are capital and not deductible from rent. They are relieved through Capital Gains Tax when you sell (GOV.UK).

Where it goes on your return and in MTD

For a landlord, it belongs in legal, management and other professional fees (property) (SA105 box 27 on the UK property pages), and in the matching category of a Making Tax Digital property update.

Most sole traders now use the cash basis, the default from the 2024/25 tax year, which counts a cost when you pay it. On traditional accounting you count it when you incur it, and equipment you keep goes through capital allowances rather than expenses.

How much an allowable cost saves

The value of a deduction is the tax it removes from your profit, not the cost itself. At the basic rate a sole trader saves 26p for every pound of allowable expense, at the higher rate 42p, and in the personal allowance taper between £100,000 and £125,140 as much as 62p. Landlords pay no Class 4 on rental profit, so they save 20p or 40p.

What £1,000 of allowable expense saves a sole trader in 2026/27

• Basic rate (20% + 6%)£260
• Higher rate (40% + 2%)£420
• Additional rate (45% + 2%)£470
• Allowance taper band (60% + 2%)£620

Records to keep

Keep invoices that describe the work or service, the tenancy agreement, agent statements and, for major work, before and after photos. Keep capital costs with the property’s purchase records, because they reduce any capital gain when you sell. Records must be kept for at least five years after the 31 January deadline for the tax year.

From 6 April 2026, sole traders and landlords with qualifying income over £50,000 keep these records digitally and send quarterly updates under Making Tax Digital, falling to £30,000 from April 2027 and £20,000 from April 2028. The MTD requirement checker shows when it applies to you.

Common mistakes

• Deducting a lease extension premium from rent.
• Deducting legal fees for extending your own lease.
• Losing the extension records needed for Capital Gains Tax.

Related expenses

This item sits in the legal, management and other professional fees (property) category, alongside accountancy fees, legal fees, letting and estate agent fees and tax investigation insurance. The A to Z of expenses answers the same question for every other cost.

TapTax sorts each cost into the right category as you record it, applies the business share where you set one, and keeps the receipts with the figures, ready for your quarterly updates and final return.