Client sold several batches of restricted stock units that were vested in prior years.  On the broker's Supplemental Information page, most of the transactions list a smaller amount in the adjusted cost or other basis column than what is listed in the ordinary income reported column.  This is a publicly traded stock and I don't find any stock splits in the company's history.  Everything I can think of would increase the cost basis, such as fees, disallowed wash sales, etc.   What could cause the adjusted cost basis to be less than the ordinary income that was recognized on the W-2 (in prior years)?