Guides / Capital Gains Tax on your return

Capital Gains Tax on your Self Assessment return (2025-26)

For 2025-26 returns (sales from 6 April 2025 to 5 April 2026). Checked against GOV.UK, HMRC's 2026 SA108 form and notes, and HMRC manuals, October 2026.

If you sold shares, crypto, a second home or a buy-to-let, you may owe Capital Gains Tax. The first £3,000 of gains is tax-free. Above that you pay 18% on the part that fits in your unused basic rate band and 24% on the rest. You report it on the Capital gains summary pages (SA108) and pay by 31 January 2027.

The £3,000 tax-free allowance

Everyone gets an annual exempt amount. For 2025-26 it's £3,000. It's the same for 2026-27. You only pay tax on your total gains for the year, after losses, above this amount.

You don't take it off yourself on the return. HMRC gives it to you automatically. There's no box for it.

The 2025-26 rates

The rates changed on 30 October 2024. Since then, the main rates are the same for every kind of asset. For 2025-26:

Type of gain	Within your basic rate band	Above it
Shares, crypto and most other assets	18%	24%
Residential property (second home, buy-to-let)	18%	24%
Gains qualifying for Business Asset Disposal Relief or Investors' Relief	14%

So for 2025-26 residential property is taxed at the same rates as shares. Before 30 October 2024 it had its own higher rates.

How your income decides the rate

Work out your taxable income. That's your income minus your Personal Allowance (£12,570 for most people) and any other reliefs.
The basic rate band for 2025-26 is £37,700. Take your taxable income off this. What's left is your unused basic rate band.
Take £3,000 off your total gains.
Gains that fit in your unused basic rate band are taxed at 18%. The rest are taxed at 24%.

If you're a higher or additional rate taxpayer, all your taxable gains are at 24%. A big gain doesn't push your income into a higher Income Tax band. It only affects the Capital Gains Tax rate.

When you must fill in the Capital gains summary

If you already send a tax return, you need the SA108 pages if any of these apply for 2025-26:

your gains, before taking off any losses, were more than £3,000
the total you sold or disposed of chargeable assets for was more than £50,000, even if you made no taxable gain
you want to claim a capital loss, or make a claim or election

You don't need the pages if all you sold was your car, personal belongings worth up to £6,000 each, shares in an ISA or PEP, gilts or Premium Bonds, or your main home with full Private Residence Relief.

Giving something away, swapping it, or selling crypto for another crypto all count as disposals. Gifts to your husband, wife or civil partner usually have no tax to pay.

Working out a gain

For each asset, your gain is:

Gain = what you sold it for − what you paid for it − costs of buying and selling − improvements

Buying and selling costs include solicitors' and estate agents' fees, stockbroker or platform dealing fees, Stamp Duty and Stamp Duty Land Tax.
Improvements must still be reflected in the asset when you sell, such as an extension. Normal upkeep like decorating doesn't count.
You can't deduct mortgage or loan interest.
If you were given the asset, or sold it to a relative, you usually use its market value instead of the price.

Add up the gains on everything you sold in the tax year, then take off your losses.

Worked example: a basic-rate taxpayer whose gain straddles the band

Sam earns a salary of £40,000 in 2025-26 and has no other income. In 2025-26 Sam sells some shares (not in an ISA) for £30,050. Sam bought them for £9,950 and paid £50 dealing fees when buying and £50 when selling.

Step	Amount
Sale price	£30,050
Less purchase price and fees (£9,950 + £50 + £50)	−£10,050
Gain	£20,000
Less annual exempt amount	−£3,000
Taxable gain	£17,000
Taxable income (£40,000 − £12,570)	£27,430
Unused basic rate band (£37,700 − £27,430)	£10,270
£10,270 at 18%	£1,848.60
£6,730 at 24%	£1,615.20
Capital Gains Tax	£3,463.80

The gain is over £3,000, so Sam must report it. These are listed shares, so on the SA108 Sam puts 1 in box 23, £30,050 in box 24, £10,050 in box 25 and £20,000 in box 26. HMRC takes off the £3,000 and works out the tax. It's due by 31 January 2027.

Losses

You can claim a loss when you sell something for less than you paid. You must report it to HMRC within 4 years of the end of the tax year you sold it in. You claim it on your return.

Losses from the same tax year are taken off your gains for that year in full. This happens even if it takes your gains below £3,000, which wastes some of the allowance.
Losses brought forward from earlier years are only used to bring your gains down to £3,000. The rest carry forward to later years.
A loss on something you gave or sold to a relative or other connected person can only be set against gains on disposals to that same person.
You can't claim a loss on something you gave or sold to your husband, wife or civil partner.

Example

In 2025-26 you make a £8,000 gain on crypto and a £1,000 loss on shares. You have £10,000 of losses from earlier years.

Gains this year minus losses this year (£8,000 − £1,000)	£7,000
Brought-forward losses used to bring this down to £3,000	−£4,000
Left, covered by the £3,000 allowance	£3,000
Tax to pay	£0
Losses still to carry forward (£10,000 − £4,000)	£6,000

You'd put £4,000 in box 45 and £6,000 in box 47.

Selling a UK home that isn't your main home: the 60-day return

If you sell a UK residential property, such as a buy-to-let or second home, and there's Capital Gains Tax to pay, you must report and pay within 60 days of completion. You do this through a Capital Gains Tax on UK property account on GOV.UK, not on your tax return. You may have to pay interest and a penalty if you're late. If your total gains are under the £3,000 allowance, UK residents don't need to make this return.

If you're in Self Assessment, you must also put the sale on your tax return. The return then works out your Capital Gains Tax for the whole year and takes off what you already paid:

Include the sale in the residential property section (boxes 3 to 7) as normal.
Put the gain or loss you reported on your 60-day returns in box 9.
Put the tax you were charged on those returns in box 10.
Give the reference number of each 60-day return in box 54.

If you paid too much on the 60-day return, HMRC sets the extra against your other Self Assessment tax. Anything still left over isn't paid back automatically. You need to ask HMRC for it.

Example

A higher-rate taxpayer sells a buy-to-let flat in July 2025 and makes a £40,000 gain after costs. They pay 24% of £37,000 (£40,000 minus the £3,000 allowance), which is £8,880, on the 60-day return. On the SA108 they put £40,000 in boxes 6 and 9, and £8,880 in box 10. If that was their only gain, the return shows £8,880 of Capital Gains Tax with £8,880 already paid, so there's nothing more to pay. If they also sold shares later in the year, the tax on those is due by 31 January 2027.

Selling your own home: Private Residence Relief

You usually pay no Capital Gains Tax when you sell your home. You get Private Residence Relief in full, automatically, if all of these apply:

it's your only home and you lived in it as your main home the whole time you owned it
you didn't let any part of it out (a lodger who shares your living space is fine)
you didn't use part of it only for business
the grounds, including buildings, are under 5,000 square metres
you didn't buy it just to make a gain

If not, you may get part relief. You always get relief for the last 9 months you owned a home that was your main home at some point. If you let out your former home, relief is usually given for the time you lived there plus those last 9 months. Letting Relief of up to £40,000 only applies if you lived there at the same time as your tenants.

If you have some gain left to pay tax on, put code PRR (or LET if Letting Relief applies) in box 8. Owners of more than one home can nominate which is their main home, within 2 years of the mix of homes changing.

Crypto

Crypto is taxed like other assets. A disposal includes selling it, swapping it for another token, spending it and giving it away. You work out the cost using a pool for each type of token, with special rules for tokens bought the same day or within 30 days after a sale. Exchange reports help, but they don't track your pooled costs, so keep your own records.

Crypto has its own section on the 2026 SA108: boxes 13.1 to 13.8.

Business Asset Disposal Relief and the Budget 2026 changes

If you sell all or part of your business, or shares in your own trading company where you've held at least 5% and worked for at least 2 years, Business Asset Disposal Relief may lower the rate:

Date you sell	Rate	Lifetime limit
6 April 2025 to 5 April 2026 (2025-26 return)	14%	£1 million
6 April 2026 to 5 April 2027	18%	£1 million
From 6 April 2027 (announced at Budget 2026)	18%	£500,000

The £500,000 limit counts relief you've already claimed in the past. Budget 2026 also announced a new Founders' Relief: a 10% rate on up to £10 million of lifetime gains for founders and early investors who held at least 25% of a high-growth company from when it started trading. It's planned for sales from 6 April 2027 and is still being consulted on. Neither change affects your 2025-26 return.

On the 2025-26 SA108, gains claiming the relief go in the "Other property, assets and gains" section (box 17, split in boxes 17.2 to 17.4), even if they're shares. Put code BAD in box 20, the qualifying gains in box 50 and your lifetime total claimed in box 50.1.

Which SA108 boxes to use (2026 form)

The paper form numbers below match the 2026 SA108 for 2025-26. The online return asks the same questions under "Capital gains summary". Fill in the section that matches what you sold. You must also attach your workings for each gain or loss.

What you sold	Section and boxes
Residential property (buy-to-let, second home, part-relieved main home)	Residential property and carried interest: number of disposals box 3, proceeds box 4, costs box 5, gains box 6, losses box 7, claim code box 8
UK residential property already reported on a 60-day return	Also box 9 (gains or losses reported) and box 10 (tax already charged)
Crypto	Cryptoassets: boxes 13.1 to 13.8 (gains 13.4, losses 13.5)
Other property and assets (land, commercial property, valuables), and anything claiming Business Asset Disposal Relief	Other property, assets and gains: boxes 14 to 22 (gains 17, losses 19, claim code 20)
Listed shares, unit trusts and OEICs	Listed shares and securities: boxes 23 to 30 (gains 26, losses 27, claim code 28)
Unlisted shares, including AIM shares, EIS, SEIS and employee shareholder shares	Unlisted shares and securities: boxes 31 to 44 (gains 34, losses 35, claim code 36)
Losses brought forward and used this year	Box 45
Losses to carry forward	Box 47
Tax already paid through the 'real time' Capital Gains Tax service	Boxes 12, 13.8, 22, 30 or 38, next to the matching section
Estimates or valuations used	X in box 53, with details in box 54

Gains go in before losses: put gains and losses in their own boxes, not a net figure. Don't take off the £3,000 allowance anywhere.

When to pay

Capital Gains Tax for 2025-26 is due by 31 January 2027, as part of your balancing payment. It isn't included in your payments on account for the next year. The 60-day property tax is the exception, because you pay it when you report the sale.

You can also use HMRC's 'real time' Capital Gains Tax service for gains other than UK homes. For 2025-26 that means reporting by 31 December 2026. If you're in Self Assessment, you still put those gains on your return.

Sold something this year? The calculator now works out your Capital Gains Tax alongside your Income Tax, using your real basic rate band, and shows which SA108 boxes to fill in. It also handles Business Asset Disposal Relief, Investors' Relief, Private Residence Relief for a home you lived in part of the time, and EIS or SEIS shares held for 3 years, as well as student loan repayments.

Work out my figures - free

Sources

General guidance, not tax advice. The examples assume the standard Personal Allowance and no other income or gains.