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Capital Gains Tax Guide 2025: Help for UK Tax Payers

Cut through CGT jargon: learn when tax applies, how to work it out and file your return on time.

How to Calculate, Report & Pay CGT Without the Stress

Sell a UK property for more than it cost and you may owe Capital Gains Tax (CGT). Work out the gain, claim any reliefs and file the 60-day HMRC CGT return to avoid penalties.

1. What Capital Gains Tax Covers — From Property to Cryptocurrency

CGT sounds scary, yet it’s simply a tax on the profit (“gain”) you make when you sell or gift certain assets. The rules cover far more than bricks and mortar, so let’s start with the full picture.

In the UK, you might pay CGT on property, CGT on shares, CGT on cryptocurrency and even CGT on business sale. HMRC treats each asset class slightly differently, but the basic steps are the same: work out the sales proceeds, subtract what you originally paid (plus buying and selling costs), then deduct any reliefs or annual allowance. The rate you pay depends on whether you’re a basic- or higher-rate Income Tax payer.

  • Residential property attracts an 18 % or 24 % CGT rate (2024/25 figures).
  • Most other assets, such as shares, are taxed at 10 % or 20 %.
  • The 2024/25 annual exemption is £3,000 (down from £6,000 last year).

Example: You bought a buy-to-let in 2012 for £200 000 and sold it in 2025 for £350 000. After £5 000 estate-agent fees and £1 000 legal costs, the gain is £144 000. Knock off the £3 000 allowance and you’re taxed on £141 000.

2. Step-by-Step: Calculate Your Gain and Reduce the Bill

Before you reach for the calculator, gather proof of:

  • Purchase price (completion statement, invoices for stamp duty and legal fees).
  • Selling costs (estate-agent fees, EPC, solicitor).
  • Capital improvements — new roof, extension or loft conversion count; daily maintenance does not.

Now follow this four-step formula:

  1. Add up all sale proceeds.
  2. Subtract your “base cost” (purchase + buying expenses).
  3. Subtract improvement costs.
  4. Subtract the annual exemption and any reliefs.

Private Residence Relief (PRR) wipes out the gain for the time you lived in the property as your main home, plus the final nine months of ownership. Lettings Relief can slice up to £40 000 off the gain if you let out part of your previous main home. Use HMRC’s free online calculator, but sanity-check the numbers — its default settings rarely match real life.

Mini-case study: Carla sold her former flat after three years of renting it out. She occupied it for five of the nine years she owned it. PRR exempted 5/9 of the gain; Lettings Relief knocked off another £20 000, slashing her tax by £4 800.

3. Reporting & Paying: Your 60-Day HMRC CGT Return

Since 2020, UK residents must file an online “HMRC CGT on UK Property” return within 60 days of completion. Miss the deadline and late-filing penalties start at £100, plus daily fines and interest.

You will need:

  • Government Gateway ID.
  • Property address and postcode.
  • Dates of purchase and completion.
  • Detailed gain calculation and reliefs claimed.
  • Estimated taxable income for the tax year (to set the CGT rate).

Once HMRC issues a payment reference, pay online or via Faster Payments. You must still list the gain on your Self-Assessment return the following 31 January so HMRC can reconcile anything under- or over-paid.

Short on time? The SwiftCGT: Online fixed-fee service lets chartered accountants handle the calculation and 60-day filing for you — £299 for a sole owner, £449 for joint owners. Returns are submitted within three working days, so you stay penalty-free.

4. Beyond Bricks: Shares, Crypto & Business Sales Explained

The 60-day rule only applies to UK residential property. For other assets, note the key differences:

  • CGT on shares: Use “share pooling” to average purchase costs. Trading fees and stamp duty are deductible. Report gains via Self-Assessment by 31 January.
  • CGT on cryptocurrency: HMRC treats crypto as an asset, not currency. Keep a wallet-by-wallet record of disposals, airdrops and gas fees. Specialist software such as Koinly or CoinTracker can export HMRC-friendly reports.
  • CGT on business sale: Entrepreneurs’ Relief (now Business Asset Disposal Relief) can cut CGT to 10 % on the first £1 million of lifetime gains if you owned the company for two years. Ask for clearance before you sell.

Tip: Use “bed and ISA” or “bed and spouse” strategies before 5 April to use each partner’s allowance and reset the base cost on shares or funds.

[Related: How to report crypto gains step-by-step](/crypto-cgt-guide)

External resource: The Office of Tax Simplification’s 2022 report (OTS) predicts further threshold cuts, so plan early.

5. Common Mistakes & Time-Saving Tools

You can avoid most CGT headaches with three golden rules: record-keeping, timing and expert help.

  • Mis-timing the sale: Contracts exchanged on 3 April 2025 and completed on 6 April push the gain into the next tax year, giving you a fresh allowance.
  • Ignoring refurb costs: Scan invoices into cloud folders on the day you pay them. HMRC accepts PDFs.
  • DIY gone wrong: One in four property sellers calculates the gain incorrectly (HMRC data, 2023). A professional review costs less than a late-filing fine.

Useful tools:

  • HMRC CGT calculator (quick estimate).
  • Google Sheets template for cost tracking.
  • SwiftCGT’s online portal for document upload and accountant chat — no office visits.

Key Takeaways

  • Work out your gain, deduct reliefs and apply the current CGT rates.
  • File the 60-day HMRC return for UK property to dodge penalties.
  • Keep digital records and consider a fixed-fee service if time is tight.

TL;DR Summary

Sell a UK property or other asset and you may face CGT. Calculate the gain: sale price minus purchase cost, selling fees and improvements. Claim Private Residence or Business Asset Disposal Relief where allowed, then subtract the annual exemption. UK property gains must be reported and paid within 60 days; everything else goes on Self-Assessment. Keep receipts, plan the timing and use a service like SwiftCGT for stress-free compliance.

Team Swift