You will have to pay taxes on the amount you sold for profit. So if you bought 150 shares at $1 for $150 and then you sold 100 shares at a $1.50, you still have to pay taxes on the $50 you made on that transaction. Even though you only got back what you put in - because you still own the other 50 shares that you haven't sold yet. When you report it you will put it in as:
Cost basis: $100 (100 shares bought at $1)
Gross Proceeds: $150 (100 shares sold at $1.50)
Total Gain/Loss: $50
Any shares you "keep" and don't sell are not considered a capital gain.
There are realized and unrealized gains. Realized gains are the ones where you sell and made a profit - those are the ones you have to report. Unrealized gains are any gains in your portfolio that you own that you are up on but haven't sold yet - you do not have to pay taxes on those until you sell them.
The only time you pay taxes on unrealized gains is when you chose the mark to market method (MTM) which I am sure you are not using.
Bottom line - anything you sell, whether you lost money or made money, you have to report. If it was a gain you will pay taxes on it.
Anything you don't sell - even if it is your free shares - you don't pay any taxes on them no matter how much they go up until you sell them.
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