You have a double safeguard. . .your brokerage plus Microsoft excel. Don't know absolutely ALL DETAILS, but there are set tax rates based on the level of your cap. gains (15% or 20% or thereabout). You 'clear' $100,000 profits--cap. gains--thru the year. . .you'll pay Uncle Sam that rate, $15,000 or $20,000. You could have losses to help offset that tax liability. . .to lessen the pay rate.
Suffice it to say, "If you do make a whopping amount, GET WITH YOUR ACCOUNTANT and let him/her advise you HOW to handle you tax exposure." It's possible you might have to pay YOUR STATE some of these profits (generally small). . .get with your accountant/tax preparer. (You do not want to make a mistake in handling this).
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