hmrc cgt calculator

What this HMRC CGT calculator is for

If you have sold a UK chargeable asset and want a quick estimate of your Capital Gains Tax (CGT), this tool gives you a practical starting point. It follows the core HMRC logic: calculate your gain, deduct allowable costs and losses, apply the annual exempt amount, then apply CGT rates based on your available basic rate band.

This is especially useful when planning for:

• Sale of a buy-to-let or second property
• Disposal of shares and funds outside tax wrappers
• Crypto gains
• General year-end tax planning before filing Self Assessment

How UK Capital Gains Tax is calculated (step by step)

1) Work out your capital gain

Start with sale proceeds, then subtract your purchase price and allowable costs:

• Acquisition costs (for example stamp duty and legal fees)
• Disposal costs (estate agent and legal selling costs)
• Capital improvement costs (not routine repairs)

2) Deduct brought-forward capital losses

If you have unused losses from earlier years that were properly reported, they can reduce your gain.

3) Apply your Annual Exempt Amount (AEA)

Individuals can usually deduct an annual tax-free allowance from gains before CGT is charged. This calculator defaults to £3,000, which you can change if tax rules update.

4) Apply the correct CGT rates

The rate depends on the asset type and how much of your basic income tax band is unused. In simple terms:

• Residential property gains: lower and higher CGT rates are used (modelled here at 18% and 24%)
• Other assets: lower and higher CGT rates are used (modelled here at 10% and 20%)

The calculator estimates how much of your taxable gain falls into the lower-rate portion of the band, and how much is charged at the higher rate.

Allowable costs people commonly miss

Many taxpayers overpay because they miss deductible items. You may be able to include:

• Solicitor and conveyancing costs on purchase and sale
• Stamp Duty Land Tax paid when buying a property
• Surveyor and valuation fees connected to acquisition/disposal
• Estate agent and platform selling fees
• Enhancement expenditure that improves or extends the asset

Routine repairs and maintenance are usually not treated as capital improvements for CGT purposes.

Reporting to HMRC: key deadlines

UK residential property sales

If CGT is due on UK residential property, a return and payment are typically required within a short post-sale window (commonly 60 days from completion under current rules).

Other asset disposals

Gains are usually reported via your Self Assessment tax return for the relevant tax year, with tax payable by the normal balancing payment deadline.

Example quick calculation

Suppose you sell an investment property for £350,000. You bought it for £220,000. Combined buying/selling costs are £11,000 and improvements are £15,000. Your gain before losses is £104,000. If you have £4,000 losses brought forward, that leaves £100,000. After a £3,000 annual exempt amount, taxable gain is £97,000. Your final CGT depends on your taxable income and remaining basic rate band.

Ways to reduce your CGT legally

• Use all available allowable costs and keep clear records
• Use carried-forward losses efficiently
• Consider timing disposals across tax years
• Use tax wrappers (ISAs/pensions) for future investing where appropriate
• Review whether specific reliefs may apply in your case

Frequently asked questions

Do I pay CGT when I sell my main home?

Often no, if full Private Residence Relief applies. Partial relief or exceptions can apply in mixed-use or letting scenarios.

Does this apply to crypto gains?

Yes, crypto disposals are generally within CGT rules for individuals, but identification/matching rules can be complex.

Can married couples reduce CGT?

In some circumstances, transferring assets between spouses or civil partners before sale can improve use of allowances and rate bands. Professional advice is recommended before transferring ownership.

Is this calculator an official HMRC tool?

No. It is an educational estimator designed to help with planning. Always confirm numbers with HMRC guidance or a qualified tax adviser.

Final note

A good HMRC CGT calculator helps you estimate liability early, avoid surprises, and plan cash flow before deadlines. Use this as a first-pass estimate, then validate your final figures with up-to-date HMRC rules.