@vfx282828 wrote:
if someone day trades, how would they not be able to take all gains in the same year
The wash sale rule does not disallow gains. It disallows certain losses. You always take all gains in the year that they occur.
I can't comment on what you might "have heard" without any details. What you "have heard" might be mistaken, or the day trader might have actually had a large net gain for the year, or the day trader might not have calculated gains and losses correctly. Handling wash sales gets very complicated when there are a large number of transactions.
You might find the detailed explanation at the following link helpful.
The Wash Sale Rule
