Capital Gains Tax Form Template for the UK

You need to complete a Capital Gains Tax form when you've made a profit selling chargeable assets in the UK tax year. Common triggers include selling a buy-to-let or second residential property, inherited assets, significant shares or investments held outside an ISA, or valuable personal items worth over £6,000 like art or antiques.

Deadlines depend on what you sold. For most gains you report through your Self Assessment return by 31 January following the tax year in which you sold the asset. For UK residential property, you usually have to report the gain and pay any tax due within 60 days of completion using HMRC's online Capital Gains Tax on UK property service, on top of any later Self Assessment filing. The UK tax year runs from 6 April to 5 April, so a sale in April can fall either side of a year boundary and change which deadline applies. Missing either deadline can lead to penalties.

Keep detailed records of purchase prices, improvement costs, selling prices, and dates, since you'll need these figures to calculate your taxable gain accurately. Note the market value of any asset you gave away or sold below market rate, because HMRC uses value rather than the amount you received in those cases. HMRC updates its guidance and digital filing routes regularly, so confirm the current process for the 2025 to 2026 tax year before you submit. You can check deadlines and file online at GOV.UK Capital Gains Tax.

• The standard SA108 Capital Gains summary pages of your Self Assessment tax return, used for most gains like share or property sales
• The Capital Gains Tax on UK property digital service, for reporting residential property sales within 60 days of completion
• The 'Real Time' Capital Gains Tax service, for reporting other gains outside a Self Assessment return
• Helpsheet HS283, which helps calculate private residence relief when selling your home
• Helpsheet HS275, for calculating business asset disposal relief (formerly entrepreneurs' relief)
• Trust and Estate Capital Gains supplementary pages, used by trustees reporting gains on trust assets

Most of these are now filed digitally through your online HMRC account, though the SA108 remains available as a downloadable page. You can find the current versions on the GOV.UK Self Assessment forms collection, which is updated each tax year.

• Individual Investors: People who sell shares, bonds, or other investments outside of tax-free wrappers like ISAs must report their gains
• Property Owners: Those selling second homes, buy-to-let properties, or inherited real estate need to declare profits
• Business Owners: Entrepreneurs selling their companies or business assets must report gains using specific relief forms
• Trustees: Responsible for reporting gains made on trust assets and investments
• Tax Accountants: Help clients calculate gains, apply relevant reliefs, and complete forms accurately for HMRC submission

• Purchase Records: Gather the original purchase price, dates, and any costs of buying the asset
• Sale Details: Document the sale price and date, plus any fees or costs related to the sale
• Market Value: Where you gave the asset away or sold it below market rate, record its market value at the date of disposal, since HMRC bases the gain on value rather than the amount received
• Improvement Costs: Collect receipts for any improvements made to property or valuable items
• Previous Claims: Note any past capital losses or unused reliefs you can offset
• Income Position: Check your Income Tax band for the year, since it affects the rate you pay on gains
• Supporting Documents: Keep contracts, invoices, and correspondence about the transaction, including any email confirmations from your broker or conveyancer
• Calculations: Work out your gain using HMRC's approved methods and, for property, the Capital Gains Tax computation working sheet

Once you have these details, enter them into the digital SA108 pages or the online property service. For the 2025 to 2026 tax year, complete the relevant pages, apply any reliefs, and make any payment due by the deadline that matches the asset you sold. If your situation is unusual, you can request a non-statutory clearance from HMRC or contact its helpline to confirm the treatment before you file.

• Personal Details: Full name, address, National Insurance number, and UTR (Unique Taxpayer Reference)
• Asset Information: Description of asset sold, including type, location, and any identifying details
• Transaction Dates: Precise acquisition and disposal dates following HMRC's tax year format
• Financial Details: Purchase price, selling price, and itemised allowable costs
• Relief Claims: Specific sections for any tax reliefs being claimed, with supporting calculations
• Declaration Section: Signed statement confirming the information's accuracy under HMRC requirements

A Capital Gains Tax form and a general Declaration Form both report information to authorities, but they serve different purposes. Here's how they compare.

GenieAI drafts, reviews, and turns around the commercial contracts behind your deals, from an asset purchase agreement to a shareholder agreement, so the underlying transaction is documented cleanly before any tax reporting follows.