Are you familiar with Section 83(b) of the tax code? It provides a method to save your clients money on their tax bill should they own stock options through their employer.
With an election made under Section 83(b), the taxpayer agrees to pay taxes on the current value of shares after exercising the option, even if the taxpayer doesn't have full ownership of the shares now because they are restricted. Restricted shares are shares of stock that cannot be sold right away due to either vesting rules or because there is a lock up period in effect.
Using the election will usually generate a current tax liability, unless the current value of the shares is only slightly more than option price or the person has an incentive stock option instead of a nonqualified stock option.
The advantage to claiming this election is that the election qualifies the person for a lower capital gains tax on any appreciation between now and when the person sells - the taxpayer could owe the government only 20 percent of the profit versus a maximum of 39.6 percent without taking the election.