This tool aims to help individuals with capital gains coming from employement equity grants and personal index funds and stock investments, in particular by performing the section 104 calculations.

You still need to check that these calculations are correct yourself, and that calculations are applicable to your tax situation. Examples of where this may not apply to you:

• You have overlapping holdings across multiple brokers.
• You have not been tax domiciled in the UK for the entire duration of your investments.

CGT Calculator takes no responsibility or liability for your tax return.

See the HMRC guidance on this topic. In short, when you sell a share, the gain that is made by this sale is calculated by considering the "average cost" of the pool of shares that you hold. This "pool" is defined by the Section 104 rules, which consider as part of the same pool:

• Any shares aquired on the same day (Same Day rule)
• Any shares aquired in the following 30 days (Bed and Breakfast rule)
• The remaining "pool" of shares is described as a "section 104 pool"

CGT Calculator aims to help with this calculation, which can be tricky in itself, but is further complicated by:

• Part disposals (i.e. selling part of your stock, rather than all in one sale)
• Accumulation funds with re-invested dividends
• Stock splits
• Spouse gifting
• Grant / Vest dates
• Currency conversion
• Legacy broker export formats

There are also many cases which CGT Calculator cannot help with, such as:

• Certain ETP (Employee Trading Programs)
• Holding the same stock across overlapping brokers (e.g. holding AAPL in multiple brokers)

The output of CGT explains the calculation is full and can be shared with a tax advisor.

To make most use of your capital gains allowance, you might want to sell up to the capital gains limit each year.

CGT Calculator includes this in the output report, i.e. how much would need to be sold to reach the capital gains limit for this year, assuming you have no other capital gains.