More than half of public companies that provide equity compensation to workers offer an employee stock purchase plan, according to the National Association of Stock Plan Professionals.
Fidelity found that only one-third of employees who have access to such plans use them.
"In many cases, it is a matter of employees not understanding the plan, the benefits of participation and the tax considerations — all of which are, admittedly, complicated," said Barbara Baksa, National Association of Stock Plan Professionals' executive director.
Here's how the taxes work for qualified employee purchase plans:
- You do not owe any taxes when you buy company stock through a plan.
- When you sell company stock, the discount that you received buying the stock is generally considered additional compensation, so you have to pay taxes on it as regular income.
- If you hold the stock for less than a year before you sell it, any gains are considered compensation and taxed at ordinary income tax rates.
Let's say you are in the 25 percent federal income tax bracket and you bought shares of your company for $85 in an employee purchase plan, discounted by 15 percent from $100 per share. You sell immediately. Your gain of 15 percent would be taxed at a 25 percent rate, so you only pocket an 11.25 percent return.
Some plans have sales restrictions on when you can sell your company stock, usually six-month or 12-month limits.
If you hold the shares for more than one year, any profit will be taxed at long-term capital gains rates, which are lower than income tax rates.
Under Trump's tax plan, capital gains tax rates would be similar though he has proposed reducing the current seven federal income tax brackets to three with rates of 12 percent, 25 percent and 33 percent. That means if Congress passes tax reform that cuts individual rates next year similar to Trump's proposal — and that's a big if — sales of company stock held for less than a year would be taxed at a lower rate than they are now for most people.
More than half of people hold on to the company shares they buy in employee stock plans, according to Fidelity. Among those that sold stock they acquired through their plan, 40 percent held the stock for more than two years.
"We don't have a lot of flippers in these plans," Cervino said.
(Disclosure: Fidelity administers the stock purchase plan for Comcast, the parent company of CNBC.)