Generally, no deduction is available for the cost of acquiring the cryptoassets from an airdrop or a hard fork, as you will not have incurred a cost in acquiring them. A deduction may be available in some limited cases when you are taxed both on receipt and also disposal. If you think this applies to you, see our guidance for further information.
Qb 21/06 Income tax - tax treatment of cryptoassets received from an airdrop
QB21/07 Income tax - tax treatment of cryptoassets received from a hard fork