The term restricted stock unit (RSU) refers to a form of compensation issued by an employer to an employee in the form of company shares. Restricted stock units are issued to employees through a vesting plan and distribution schedule after they achieve required performance milestones or upon remaining with their employer for a particular length of time
Part of RSUs are sold as reserved tax. If your final sell price is lower than vesting price, you can claim capitol Loss on your sold shares. Otherwise, you have capital gain.