Selling ESPP or stock rewards or dividends

Yes. When you sell the ESPP stock relatively soon, it is taxed as ordinary income. If you hold the stock, it can be taxed as a more favorable capital gain. The rules for statutory stock options (ISO and ESPP) are:

• One year after the stock was transferred to the taxpayer or
• Two years after the option was granted

I want to urge you to create a financial notebook that is kept separate from your tax return. Keep it safe and each year, add your year-end statements from all your financial accounts plus a copy of your W2’s, 5498, and any 8606 forms. 

This will protect you down the road as proof of your basis in your various investments. As you go through life, rollovers, ESPP sales, and more will be captured for you. 

When you do sell, your notebook will be invaluable with knowing what was first, the order, the basis, and the lot size for stocks.