A type of stock plan that receives special tax treatment because it meets related requirements in the Internal Revenue Code. In the United States, incentive stock options (ISOs) and Section 423 employee stock purchase plans are tax-qualified. Tax rates for participants are based on how the plan is structured and how long the resulting stock is held. In some countries, tax-qualified plans (also called tax-preferred or tax-favored plans) may require special company filings with the government and official review and approval of the stock plan (see the Global Tax Guide for details).