Based on the information provided, H-1B visa holders are liable for social security (FICA) and Medicare taxes and not refundable on their departure after six years term. One way to escape applicability of above FICA and Medicare taxes is to see if you are covered under 'Totalization Agreement'. The United States has entered into social security (totalization) agreements with Canada and a few European countries to eliminate duplicate coverage and taxes on the same covered employment. A totalization agreement allows a citizen or lawful permanent resident of one country temporarily working in the other country to avoid paying that country’s social security taxes under the detached worker rule. In general, a detached worker is an individual who is on a temporary employment assignment that is anticipated to last five years or less.