@mattly it's because your purchase price from the grant is typically less than the market price. The difference is essentially a boon, extra income. Hence the tax treatment as income.
@zero Indeed, short-term gain would be taxed differently than long-term.
It seems we agree the gains from any event after exercising are taxed as gains (short or long) and only the discount on market price at exercising is taxed as wages.
So, I think the part of OP that says "gains from selling stock bought under an Employee Stock Purchase Plan count as wages” is not true, except by "coincidence".
That said, I'll look into the details as time permits. But OP is prolly right. 🙏
@smurthys@mattly What you say is essentially true: one part is taxed as wages, and one part as capital gains (long or short).
The complexity comes from where the dividing line is drawn - it depends on both the period of time from grant to exercise, and exercise to sell... I don't pretend to understand the rational for the several different cases.. but you can find decent references (and flowcharts!) on-line to help you wade through it.
@mattly I'm a bit confused. I can see why the difference between what you paid and the market price on the day the stock became yours is taxed as wages. However, the difference between that market price and the price you sold the shares at should be capital gains/loss, no?
Unless you sold at your market price, possibily even the same day the shares became yours.
It has been a while since I was in a similar situation. So, I don't really remember all the details.