Capital Gains Tax when selling a buy-to-let property

Selling a buy-to-let property, second home or former rental property can trigger Capital Gains Tax. CGT is charged on the gain, not the full sale price. GOV.UK explains that you may have to pay tax when you sell property that is not your home, including buy-to-let properties, land and inherited property, in its guide to tax when you sell property.

For UK residential property, the deadline can be much sooner than landlords expect. If CGT is due, GOV.UK says the gain usually needs to be reported and paid within 60 days of completion through the Capital Gains Tax on UK property reporting service.

That is why the CGT position should be reviewed before completion, not after the solicitor has transferred the sale proceeds.

When CGT applies to property sales

CGT commonly applies when selling a property that is not your only or main home. This can include a buy-to-let property, second home, holiday home, inherited property or land. GOV.UK’s guide to what you pay CGT on explains the types of assets and disposals that can fall within Capital Gains Tax.

You do not usually pay CGT when selling your only or main home if Private Residence Relief applies in full. However, the position can change if the property was let out, used as a second home, used partly for business, or was not your main residence for the whole ownership period.

Merranti’s guide to Capital Gains Tax and Main Residence Relief explains how CGT can arise where a property was once your home but was later rented out or used differently.

The 60-day CGT reporting rule

The 60-day reporting rule is one of the biggest practical traps for landlords.

If you sell a UK residential property and CGT is due, you normally need to report and pay the tax within 60 days of completion. GOV.UK also warns that interest and penalties may apply if UK residential property gains are not reported and paid on time through the UK property CGT reporting process.

This is separate from the normal annual Self Assessment routine. If you are already within Self Assessment, the property disposal may still need to be included on your tax return as well.

Merranti’s guide to CGT on residential property sales is a useful next read because it focuses specifically on reporting, payment and the 60-day deadline for property disposals.

How to work out the gain

CGT is based on the gain, not the amount of cash left after the mortgage has been repaid. GOV.UK explains in its Capital Gains Tax overview that it is the gain you make that is taxed, not the amount of money you receive.

A simple property CGT calculation usually starts with the sale proceeds, then deducts the purchase cost, allowable buying and selling costs, qualifying improvement costs, available losses, and any reliefs.

A basic structure is:

• sale proceeds
• less original purchase price
• less buying costs
• less selling costs
• less qualifying improvement costs
• less available reliefs and losses
• less annual exempt amount
• equals taxable gain

Not every cost reduces the gain. For example, estate agent and legal fees on sale may be relevant, and capital improvements may be relevant, but normal maintenance and repairs are usually treated differently.

Merranti’s article on allowable expenditure for Capital Gains Tax relief explains why the distinction between repair costs and capital improvements matters.

CGT annual allowance and rates

For 2026/27, the CGT annual exempt amount for individuals is £3,000. GOV.UK lists the current figures in its Capital Gains Tax rates and allowances guidance.

CGT is only charged on gains above the available annual exempt amount, after deducting any allowable losses and applying any available reliefs.

The rate of CGT depends on the taxpayer’s income position and the type of gain. GOV.UK explains the current position in its Capital Gains Tax rates guidance.

This interaction with income tax matters. A landlord with employment income, pension income, dividends or self-employment profits may already use part or all of the basic-rate band before the property gain is added.

Merranti’s broader guide to CGT allowances, rates and planning considerations is useful supporting content for readers who want the wider context beyond residential property.

Private Residence Relief and former homes

If the property was once your main home, Private Residence Relief may reduce the taxable gain. GOV.UK explains how the rules can apply where you have let out part or all of your home.

This can be important for accidental landlords. For example, someone may have bought a flat, lived in it for several years, then moved out and rented it before eventually selling it. In that situation, the whole gain may not be taxable, but the calculation needs to be split between qualifying and non-qualifying periods.

Merranti’s Main Residence Relief guide explains the main conditions and common traps around properties that were used as homes for only part of the ownership period.

Common CGT mistakes landlords make

The first mistake is assuming CGT is based on the cash left after the mortgage is repaid. Mortgage repayment affects cash flow, but it is not normally part of the gain calculation.

The second mistake is missing the 60-day deadline. Landlords who wait until the next Self Assessment deadline may already be late if CGT was due on a UK residential property sale. GOV.UK explains the reporting deadline in its guide to reporting and paying CGT on UK residential property.

The third mistake is confusing repairs with improvements. Repair costs may have been deductible against rental income at the time, but that does not automatically mean they can also be added to the property cost for CGT. Capital improvements need to be reviewed separately.

The fourth mistake is ignoring joint ownership. If a property is jointly owned, each owner needs to consider their own share of the gain. GOV.UK refers to jointly owned property in its UK property CGT reporting guidance.

The fifth mistake is leaving planning until after exchange or completion. By then, some options may be limited or unavailable.

Planning points before selling

Before selling a rental property, landlords should review:

• expected sale proceeds
• original purchase cost
• legal and estate agent fees
• capital improvement invoices
• ownership shares
• periods of main residence occupation
• rental history
• available capital losses
• other taxable income in the year of sale
• whether Self Assessment reporting is also needed

Merranti’s article on CGT strategies for landlords and second homes covers practical planning areas such as Letting Relief, partial Private Residence Relief and timing-based planning.

This does not mean transfers or timing changes should be made automatically. Property planning can also affect Stamp Duty Land Tax, legal ownership, mortgage arrangements, inheritance planning and wider tax treatment.

Speak to Merranti before completion

Selling a buy-to-let property is not just a legal transaction. It is also a tax reporting event with a short deadline.

Merranti Accounting can help estimate the gain, review allowable costs, consider available reliefs, prepare the 60-day CGT report, and make sure the disposal is reflected correctly in Self Assessment where required.

If you are selling a rental property, second home or former main residence, contact Merranti Accounting before completion.