The air drop is considered taxable income based on price of spark the day you have control over the asset. So if it was a snap shot on dec 12 2020, but it wasn’t distributed to you where you could actually trade it until feb 2021, then you would declare it on 2021 tax return.
A great example was provided. Let’s say you had 1 spark token based on dec 12 snap shot. The first day it traded it was worth $1. However you did not get control of your spark until feb 2021 and at that time it was worth $3. You then decide to sell that spark token on July 2021 when it because worth $5.
In that scenario, for your 2021 tax return, you would have to declare $3 of taxable income from air drop and $2 of capital gains from the sale of the asset.