The IRS has a concept known as the constructive receipt of income; effectively, income is not received until it is available to draw on and has been set aside to be used any time.

I never heard of this before and don't really understand what it even means. If I had to guess then it would apply to both Steem Power and Bitcoin Cash meaning people don't pay taxes until they actually receive it in some official capacity? I'm confused.

From Wikipedia:

unfettered control in determining when items of income will or should be paid.[2] Unlike actual receipt, constructive receipt does not require physical possession of the item of income in question.

So when exactly do we have constructive receipt with regard to Steemit? Is it when it's converted to Bitcoin? Is it when it's Steem Dollars? Steem Power I'm not sure about because the developers control that and can make it do whatever they want (as they have in the past modified it).

“Income although not actually reduced to a taxpayer's possession is constructively received by him in the taxable year during which it is credited to his account

What does this mean? His account?

 The United States Tax Court more concisely articulated the doctrine of constructive receipt in Davis v. Commissioner.[4] The court stated that for income to be constructively received, the funds must be made available to the taxpayer without substantial limitations.

Steem Power doesn't seem to meet the criteria of being without substantial limitations. Steem Dollars is iffy and needs more discussion. We definitely cannot do anything with Steem Power before powering it down as we are limited in our ability.