That's not how a W2 works. All of those other forms of compensation are, of course, in their 1040 but are probably on a K1 or other amendment.
Social security contributions (to pick the most important one) can only come from wage income so the question remains: how are they paying into social security and, if they are not, why is that allowed when it is generally assumed that it isn't ?
Social security contributions (to pick the most important one) can only come from wage income so the question remains: how are they paying into social security and, if they are not, why is that allowed when it is generally assumed that it isn't ?