cgt tax calculator

How this CGT tax calculator works

Capital Gains Tax is charged on the profit made when you dispose of certain assets. The taxable amount is usually not the full sale value; it is the gain after costs, losses, and allowances are applied. This calculator follows a simple framework:

• Start with net sale proceeds (sale price minus selling costs).
• Subtract your total acquisition base (purchase price plus eligible purchase and improvement costs).
• Apply losses carried forward.
• Apply your annual exemption.
• Apply any relief/discount percentage.
• Apply your CGT rate to estimate tax due.

What to include in your cost basis

Many people overpay tax simply because they forget to include allowable costs. In most cases, your cost basis can include more than the original purchase price.

Common items often included

• Purchase-related costs (legal fees, broker fees, transfer taxes where allowed).
• Capital improvements that increase value or life of the asset.
• Selling costs when disposing of the asset.

Routine maintenance is often treated differently from capital improvements, so keep records and invoices carefully.

Simple example

Suppose you bought an asset for £120,000, spent £3,500 on buying costs, and £10,000 on improvements. You later sold it for £210,000 and paid £3,000 in selling costs.

• Net sale proceeds: £210,000 - £3,000 = £207,000
• Total base cost: £120,000 + £3,500 + £10,000 = £133,500
• Raw gain: £207,000 - £133,500 = £73,500
• Then reduce by losses/exemption and apply your tax rate.

This is exactly the sequence the calculator uses so you can see each part of the result clearly.

Choosing the right CGT rate

Your applicable rate may depend on:

• Your total taxable income for the year.
• The type of asset sold (property, shares, business assets, crypto, etc.).
• Whether specific relief rules apply in your jurisdiction.

If you are unsure, run multiple scenarios (for example, 10%, 20%, 24%, or other possible rates) to create a planning range.

Ways to reduce CGT legally

• Use annual exemptions: plan timing of disposals across tax years.
• Offset losses: report and carry forward allowable capital losses.
• Track costs properly: include qualifying acquisition/disposal costs.
• Consider reliefs: certain business or main-residence rules may reduce gains.
• Plan jointly: in some countries, transfers between spouses/civil partners can improve use of allowances.

Record-keeping checklist

Good records are your best defense during filing and any audit review. Keep:

• Purchase and sale contracts
• Broker statements and completion statements
• Invoices for legal, agent, and improvement costs
• Documents supporting any claimed losses or reliefs

Important disclaimer

This calculator provides an estimate for planning purposes only. It does not replace advice from a qualified tax professional. CGT rules change regularly, and the correct result may depend on residency, ownership history, income bands, relief eligibility, and local law.