Keeping adequate records of all expenditure will help you correctly work out the amount of capital gain or capital loss you have made when a CGT event happens. It will also help to make sure you do not pay more CGT than is necessary.
You must keep records of everything that affects your capital gains and capital losses. Penalties can apply if you do not keep the records for at least five years after the relevant CGT event. If you use information from those records in a later tax return, you may have to keep records for longer. If you have applied a net capital loss, you should generally keep your records of the CGT event that resulted in the loss until the end of any period of review for the income year in which the net capital loss is fully applied.
For more information, see Taxation Determination TD 2007/2 – Income tax: should a taxpayer who has incurred a tax loss or made a net capital loss for an income year retain records relevant to the ascertainment of that loss only for the record retention period prescribed under income tax law?
Keeping good records can help your beneficiaries reduce the impact of CGT after you die. If you leave an asset to another person, the asset may be subject to CGT when a CGT event happens to that asset in the future, for example, if your daughter (the beneficiary) sells the shares (the asset) you have left her in your will.