You must report it as soon as it becomes a capital gain. You don't have to report it if it is still a loss. I didn't report it in 2019 and 2020. However, during tax year 2021, my partial distribution exceeds the remaining cost basis so I filed a report. The entire distribution I got in 2022 is 100% capital gain (because my cost basis is now 0).
So if you receive $1000 in 2022 from the liquidation of Altaba and your remaining cost basis in 2022 is $200, you have an $800 capital gain to report. Doesn't matter if this isn't final distribution. If you receive more this year, the entire 2023 cash liquidation is a capital gain you must file next year. Hope that isn't confusing.
