If you cashed in on property, shares, or any other investment this year, the paperwork isn’t quite over—HMRC wants their cut, and the SA108 form is your ticket to keeping everything above board. Whether you’re a first-time landlord, a seasoned investor, or just sold some surprise crypto gains, this is the form you’ll need for capital gains on your self assessment.
Here’s what the SA108 does, who has to use it, and how to make filing a breeze—whether you’re a UK taxpayer, non-resident, sole trader, or just someone who finally sold that family heirloom at auction.
📋 KEY UPDATES FOR 2025
CGT rates increased: For disposals after 30 October 2024, the basic rate is now 18% and the higher rate 24% for non-residential assets like shares and crypto.
Annual exemption cut: The CGT annual exempt amount is now £3,000 for 2024/25 (down from £6,000), so more gains may be taxable.
No reliefs for furnished holiday lets: From 6 April 2025, holiday lets lose Business Asset Disposal Relief, Gift Relief, and Roll-over Relief.
What is the SA108 form and who needs it?
The SA108 form is HMRC’s official way of saying, “Tell us all about your capital gains”—it’s the supplementary page you use with your main self assessment tax return to declare profits from selling assets.
Who needs to fill it out?
You’ll need the SA108 if, in the relevant tax year, you made taxable gains on:
- UK residential property or land
- Cryptoassets (including cryptocurrency)
- Listed or unlisted shares
- Business assets
- Investments (like bonds, antiques, or even that rare comic book collection)
It’s not just for investors—self-employed individuals, non-resident taxpayers, and anyone with significant asset sales or disposals may need to complete this form. If you’re claiming capital losses or deducting allowable costs (like legal fees or broker commissions), you’ll record them here too.
Online or on paper?
Filing online? HMRC’s system will prompt you for the SA108 section as you enter details about asset sales. Filing by paper? You must attach the SA108 supplementary pages to your tax return (and missing them is one of the most common reasons for HMRC follow-ups).
What counts as a capital gain?
A capital gain is the profit you make when you sell (or “dispose of”) something that’s increased in value—think of it as HMRC’s way of sharing in your investment success. The SA108 capital gains summary is where you lay it all out for the tax authorities.
Examples of assets you’ll report include:
- UK residential property and commercial property or land (except your main home, if it qualifies for private residence relief)
- Listed shares (publicly traded companies) and unlisted shares (private companies)
- Cryptoassets (including cryptocurrencies like Bitcoin or Ethereum)
- Business assets (like equipment, goodwill, or business premises)
- Personal possessions worth over £6,000 (art, jewelry, antiques—if you finally sold that giant vase from Aunt Mabel)
- Investments under schemes such as the Seed Enterprise Investment Scheme (SEIS)
Reliefs and reporting
Certain gains may qualify for reliefs—such as business asset disposal relief (formerly entrepreneurs’ relief), investors’ relief, or private residence relief (for your main home if you meet the conditions). Make sure to check eligibility and report these on the SA108.
What’s exempt from CGT?
- Your main home (if it meets all private residence relief conditions).
- Assets held within an ISA.
- Certain tax-free investments, such as premium bonds or National Lottery winnings.
What you’ll need to report
- The original purchase price (or a professional valuation if you inherited, were gifted, or acquired the asset before 1982).
- The disposal value (sale price or open market value if gifted).
- Any associated costs—legal fees, stamp duty, agent commissions, or enhancement costs (improvements, not regular repairs).
📌 Pro Tip: Keep detailed records for every asset you sell—purchase documents, valuations, improvement receipts, and sale statements—because you’ll need these figures for your capital gains summary (and HMRC can ask for proof up to six years later).
When do you need to use the SA108?
You’ll need the SA108 form if your tax year includes almost any kind of asset disposal that could trigger Capital Gains Tax (CGT)—and sometimes even when no tax is due. Here’s when to reach for the SA108:
1. Property disposal
Selling, gifting, or transferring any property or land in the UK or abroad is one of the most common triggers for the SA108 form. Even if you think the gain is covered by reliefs or exemptions, HMRC expects a full record—especially when part of the property has been used for business, rented out, or inherited.
- Main home: If you sell your main home and all or part doesn’t qualify for private residence relief (e.g., you rented out a room, used part for business, or the garden exceeds 5,000 sq m), you’ll need to report the gain—even if no CGT is due.
- Second homes and buy-to-let: All sales of second homes, buy-to-let properties, holiday lets, or inherited homes not used as your main residence must be reported, as these rarely qualify for full relief.
- Commercial property: Disposals of shops, offices, warehouses, farmland, or garages always require SA108 reporting, regardless of whether you operated as a business or private owner.
- Partial sales: If you sell just a share of a property (for example, by transferring a part interest to a family member or as part of a joint ownership arrangement), each party must declare their share of the gain.
- Gifting property: Giving away property (other than to a spouse or civil partner) counts as a disposal for CGT, including gifts due to divorce or separation settlements.
- Overseas property: UK residents must declare gains from selling foreign properties—don’t assume only UK properties count.
2. Cryptoassets and digital assets
Crypto isn’t just a currency—it’s a taxable asset in HMRC’s eyes. Every disposal or transaction, even those without a cash element, could trigger CGT and must be disclosed on the SA108 if you’re filing a self assessment.
- Selling crypto: Any sale of Bitcoin, Ethereum, NFTs, or other tokens needs to be declared, even if you made a loss.
- Swapping crypto: Swapping one crypto for another or using crypto to pay for goods/services is treated as a disposal.
- Gifting crypto: Gifting cryptoassets (unless it’s to a spouse/civil partner) is a disposal for CGT and requires SA108 reporting.
- Foreign exchanges: Trading on overseas platforms or holding assets abroad as a UK tax resident does not exempt you from reporting.
- Negligible value claims: If your crypto becomes worthless or is stolen, you may be able to claim a loss—this must also be recorded on the SA108.
If you’re cashing out of the stock market or private businesses, or even just gifting shares, you’ll need the SA108 for almost every type of share transaction. This applies to regular investors, employee shareholders, and those involved in corporate actions.
- Listed shares: Selling shares in public companies, whether held directly or in a broker account.
- Unlisted shares: Disposing of shares in a private business or startup, or gifting them (other than to a spouse/civil partner).
- Employee share schemes: Selling shares obtained through SAYE, SIP, EMI, CSOP, or unapproved options—be prepared to show acquisition and disposal details.
- Gifting shares: Gifts to anyone except your spouse/civil partner are treated as disposals for CGT and need to be reported.
- Inheritance or trust shares: Selling shares received through inheritance or as a beneficiary of a trust must be declared.
- Corporate actions: Gains from buybacks, takeovers, reorganisations, or converting shares into different types.
- Rights issues, bonus issues, scrip dividends: If you sell or otherwise dispose of shares received this way, it all goes on the SA108.
4. Business assets and interests
Selling, transferring, or winding up a business brings a raft of potential CGT reporting obligations. The SA108 ensures HMRC sees every disposal, from business premises to intangible assets like goodwill.
- Selling a business: The sale of all or part of a sole trader or partnership business, or shares in your own limited company, should be disclosed.
- Business premises or equipment: Disposals of offices, factories, plant, equipment, or business vehicles, whether sold, transferred, or scrapped.
- Ceasing self-employment: Closing down and selling off business assets triggers disposals that require reporting.
- Partnership assets: Transferring your share of partnership property, stock, or equipment to other partners or outsiders.
- Business asset disposal relief: Claims for relief (formerly entrepreneurs’ relief) or investors’ relief are made and explained on the SA108.
- Mixed-use assets: If an asset was used for both private and business purposes, only your share of the gain needs to be reported—but the calculations must be included.
5. Personal possessions and unusual assets
CGT isn’t just about big-ticket investments. Selling or giving away valuable personal items and unique assets can trigger a need for the SA108—even if you never thought of yourself as an “investor.”
- Valuable possessions: Art, antiques, jewelry, classic cars, or any other “chattel” worth over £6,000 at disposal.
- Collections: Selling off a stamp, coin, wine, or rare book collection, especially if broken into smaller lots.
- Selling in parts: Disposing of a single valuable item in stages, such as breaking up and selling pieces of an artwork or jewelry set.
- Intellectual property rights: Gains from selling the right to receive future royalties, annuities, or copyright.
- Timeshares, boats, aircraft: The sale of high-value non-land assets, including unusual or luxury items, should be disclosed if CGT applies.
If you own assets with others, or transfer ownership as part of a legal or life event, you may need to file an SA108 for your individual share—even when it seems informal.
- Jointly owned property or shares: Each owner must file their share of the gain or loss—even if you sold at the same time.
- Spouse/civil partner transfers: Transfers are often exempt, but if HMRC requests information or it’s part of a more complex arrangement (like a divorce), you may still need to report.
- Divorce or separation: Assets transferred between spouses as part of a legal settlement may require both parties to file details.
- Selling part-interest: If you sell just your share in a jointly held business or investment, that disposal goes on your SA108.
7. Special situations and compliance triggers
HMRC expects a capital gains paper trail for any situation outside the norm. This is where many edge cases appear—even if no tax is due.
- Multiple disposals: If your total proceeds from all sales (not just gains) are more than four times the CGT annual exemption, you must file—even if all gains are within the allowance.
- Inheritance, gifts, or trust property: Selling or transferring assets you received via inheritance, trust, or as a gift from someone other than a spouse/civil partner.
- Options, warrants, or futures: Exercising or disposing of rights to acquire assets (or letting them lapse) may require reporting.
- Non-resident reporting: Non-UK residents must report UK land/property sales within 60 days, plus file the SA108 in their annual self assessment.
- Chattels and foreign assets: Jointly owned crypto, art, or foreign property disposals may all require SA108 reporting.
- HMRC request: Even if you believe no tax is due, you must file the SA108 if HMRC specifically requests details.
- Mortgage, loan, or legal proof: Banks and solicitors may request SA108 evidence to verify your tax position for large transactions or legal proceedings.
📌 Pro Tip: If you’ve sold, gifted, swapped, or even given away something valuable, it’s safest to check the SA108 notes on gov.uk—and if in doubt, file the form anyway. Too much information is always safer than not enough when it comes to Capital Gains Tax.
How to complete the SA108 form (and declare your capital gains)
Filling out the SA108 isn’t just a box-ticking exercise—HMRC wants the full story for every asset you’ve sold, swapped, or gifted. Here’s how to make your capital gains return watertight, whether you’re filing online or by post.
1. Find and access the form
- Online: When filing your self assessment tax return online, add the SA108 section and follow HMRC’s prompts.
- Paper: Download the latest SA108 form as a PDF from gov.uk, or request a paper copy if needed.
2. Gather your information
You’ll need to assemble:
- Dates: Acquisition and disposal (sale/gift) dates for each asset.
- Purchase price and sale proceeds: Original cost and what you received (or market value if gifted).
- Associated costs: Legal fees, stamp duty, agent commissions, and any costs of improving the asset (not just maintenance).
- Valuations: Professional valuations, especially for inherited, gifted, or pre-1982 assets.
- Tax reliefs: Details for any relief you’re claiming—private residence relief, business asset disposal relief, entrepreneurs’ relief, or investors’ relief.
- Losses: Any capital losses to offset against your gains.
- Number of disposals: Total up each asset or portion sold.
3. Complete the relevant sections
Fill out every section that applies to you, including:
- Residential property: For sales of UK homes, buy-to-lets, or overseas property.
- Shares and securities: List all disposals of listed, unlisted, and employee shares.
- Cryptoassets: Declare all disposals, swaps, or gifts of cryptocurrency and NFTs.
- Other assets: Anything else—personal possessions, business assets, collectibles.
- Employee share schemes: Use this if you’ve sold shares acquired via SAYE, SIP, EMI, or unapproved options.
- Reliefs and losses: Clearly detail all reliefs you’re claiming and losses carried forward.
4. Attach the SA108 and any supplementary pages
- Online: The system prompts you to add the SA108; include any other supplementary forms (e.g., for property or foreign income).
- Paper: Attach your completed SA108 to the main SA100 tax return, plus any supporting evidence or calculation statements.
5. Use HMRC helpsheets and calculators
Before you fill in your SA108 or hit “submit,” consult the relevant HMRC helpsheets and use a reliable tax calculator. These resources are packed with expert guidance and can help you avoid the most common errors—even if your situation feels straightforward.
- HS283 (Private residence relief): Clarifies what qualifies for exemption when selling your main home.
- HS275 (Entrepreneurs’ relief / Business asset disposal relief): Explains how to claim and calculate these reliefs.
- HS297 (Non-resident CGT): Guides non-residents on how to report and calculate tax on UK property disposals.
- HS286 (Shares and securities): Details how to work out gains, allowable costs, and reliefs for shares and securities.
- HS307 (Cryptoassets): Helps you correctly report cryptocurrency and NFT gains or losses.
- HS325 (Losses): Outlines how to claim, carry forward, or offset capital losses from previous years.
- Tax calculator: Use HMRC’s CGT calculator or a reputable online calculator to estimate your capital gains tax and check your figures before submitting.
- HMRC website: Always download the latest helpsheets and official forms from gov.uk to ensure you’re following up-to-date guidance.
6. Real-time reporting for residential property
- UK residential property: If you’ve sold UK residential property and owe CGT, report and pay within 60 days of completion using the real time service and still include the disposal on your SA108 self assessment.
- Non-residents: Non-UK residents must always report UK property disposals within 60 days, plus on the annual SA108.
7. Filing and what happens next
- Deadlines: 31 January (online filing), 31 October (paper returns) after the end of the tax year.
- After submission: HMRC reviews your return. They may issue a calculation, accept your figures, or ask for clarification. Keep all supporting documents and records in case of queries—sometimes up to six years after submission.
📌 Pro Tip: For each disposal, keep a digital “evidence pack” that includes sale contracts, valuations, calculations, correspondence, and a copy of the exact HMRC helpsheet you relied on. If HMRC ever queries your return—even years later—you’ll have every number and document ready to back up your claim, putting you in the top 1% of prepared taxpayers.
Mistakes to avoid and how to get it right
Completing the SA108 can feel straightforward—until a small oversight snowballs into an HMRC query. Keep an eye out for these common pitfalls to ensure your total gains, tax rates, and reliefs are reported accurately:
1. Missing the SA108 when required
Many taxpayers forget to file the SA108, especially non-residents selling UK property or anyone making multiple disposals in the same tax year—even if their total gains are under the exemption.
2. Incorrect or missing valuations, dates, or prices
Entering the wrong purchase price, forgetting a professional valuation, or mixing up purchase and disposal dates can throw off your tax rates and lead to HMRC queries or extra tax.
3. Failing to claim eligible tax relief
Don’t leave money on the table—always check if you qualify for business asset disposal relief, private residence relief, or other income tax reliefs, and complete the relevant sections.
Gains from cryptoassets, NFTs, or employee share schemes often slip through the cracks—if you made a profit, report it, no matter how small.
5. Overlooking helpsheets, civil partner disposals, or number of disposals
If you skip HMRC helpsheets, miss details about assets held jointly with a civil partner, or underreport the number of disposals, you risk errors or penalties.
6. Failing to keep detailed records or misunderstanding exemptions
Incomplete records or misunderstanding what’s exempt (for example, thinking all personal items are CGT-free) can leave you unable to prove figures for total gains if HMRC asks.
File with confidence—and a smile
Got capital gains to declare? The SA108 can look intimidating, but you’ve got this! Double-check your details, claim your reliefs, and attach every required page—then pat yourself on the back for being ahead of the game.
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Frequently Asked Questions
Do I need to fill in the SA108 if my total gains are under the CGT annual exemption?
Yes, in some cases—especially if HMRC requests details, you have multiple disposals with total proceeds over four times the annual exemption, or you’re a non-resident disposing of UK property.
What counts as a “disposal” for SA108 purposes?
A disposal means selling, gifting, swapping, or even parting with an asset—property, shares, cryptoassets, business interests, or personal possessions over £6,000.
Can I include losses as well as gains on the SA108?
Absolutely! Reporting allowable losses on your SA108 can help reduce your overall CGT bill now and in future years—so don’t leave them out.
How do I file the SA108 form online?
When filing your self assessment online, the system will prompt you to add the SA108 “capital gains summary” section if you report asset sales. Simply fill in the details as you go.
I’ve sold crypto—do I really need to report it?
Yes! HMRC treats cryptoassets as chargeable assets. All disposals—sales, swaps, gifts—must be reported, even if you made a loss.
What information do I need to complete the SA108?
You’ll need purchase and sale dates, original cost, sale proceeds, any professional valuations, details of associated costs (like legal fees), and information about any reliefs or exemptions claimed.
Is real-time reporting required for property sales?
Yes, for most UK residential property sales that trigger CGT, you must report and pay within 60 days of completion and still include the disposal on your annual SA108.
Can I get help with the SA108?
Definitely. HMRC’s helpsheets on gov.uk are a good start, and a qualified accountant can make sure you claim all possible reliefs and stay compliant.
Do jointly owned assets require each owner to file an SA108?
Yes—each co-owner needs to declare their share of any gain or loss separately on their own SA108 form.
What’s the deadline for submitting the SA108?
It matches your main tax return: 31 October for paper filing and 31 January for online submissions, following the end of the tax year.