When you sell or dispose of an asset, you need to work out whether you’ve made a capital gain and, if so, how much of that gain may be subject to Capital Gains Tax (CGT). The calculation follows a straightforward formula but knowing which costs you can deduct is key to making sure you don’t overpay tax.
The Basic Formula
At its simplest, the calculation looks like this:
Proceeds of Sale – Acquisition Costs – Allowable Expenses = Capital Gain
In other words, you compare what you sold the asset for against what it cost you to acquire it, and then deduct certain expenses you incurred in buying, improving, or selling it.
What Counts as Sale Proceeds?
The proceeds of sale usually mean the amount you received when you sold the asset. However, in some cases (for example, when you gift an asset or sell at below market value), HMRC will use the market value instead.
From these sale proceeds, you can deduct costs directly linked to the sale, such as:
- Estate agent or advertising fees
- Legal fees associated with the sale
- Valuation fees
These reduce the “net proceeds” used in your gain calculation.
What Counts as Acquisition Costs?
Acquisition costs are the expenses you incurred when you originally bought or acquired the asset. These can include:
- The purchase price (or the probate value if you inherited it)
- Legal fees at the time of purchase
- Stamp Duty (SDLT for property or SDRT for shares)
- Broker or agent commissions
These costs are all deductible because they are part of the cost of securing ownership of the asset in the first place.
Enhancement Expenditure
This is a crucial category that is sometimes overlooked. Enhancement expenditure refers to money spent improving the asset during the period you owned it. To qualify as deductible, the expenditure must:
- Add value to the asset, and
- Be reflected in its condition at the time of disposal.
Examples include:
- Extensions, renovations, or improvement works on a property
- Costs of installing features that increase value (e.g. a new conservatory, structural upgrades)
- Professional or legal costs linked to preserving or defending your ownership (for example, legal fees from a boundary dispute).
It’s important to note that maintenance or repair costs do not count as enhancement expenditure — only work that genuinely improves or adds value to the asset.
Putting It All Together
When you sell an asset, your taxable capital gain will therefore be calculated as:
Sale Proceeds
➖ Selling costs (legal, advertising, valuation)
➖ Acquisition costs (purchase price, stamp duty, legal fees, commissions)
➖ Enhancement expenditure (value-adding improvements and qualifying legal/professional fees)
= Chargeable Gain
Example
Imagine you bought a rental property for £200,000. Over the years, you spent:
- £5,000 on solicitor and stamp duty at purchase
- £20,000 on a new extension (enhancement)
- £2,000 in legal fees defending a boundary dispute
You later sold the property for £350,000, paying £3,000 in estate agent and legal fees for the sale.
Here’s the calculation:
- Sale proceeds = £350,000
- Less selling costs = £3,000
- Net proceeds = £347,000
Now deduct acquisition costs and enhancements:
- Original purchase price = £200,000
- Stamp duty & legal = £5,000
- Extension = £20,000
- Boundary dispute fees = £2,000
Total deductions = £227,000
Capital Gain = £347,000 − £227,000 = £120,000
That £120,000 is your chargeable gain before applying exemptions (like the annual exempt amount) and tax rates.
Key Takeaway
When calculating capital gains, it’s not just about the difference between purchase and sale price. You should carefully include all allowable costs — purchase expenses, selling expenses, and enhancement expenditure. This ensures your taxable gain reflects your real profit, not an inflated figure.
