Generally speaking, money contributed to an HSA is before tax money. Depending on the plan setup all contributed monies must be spent on qualified medical expenses prior to March 15 (or thereabouts) of the next tax year. Any monies contributed to an HSA not used by that date for qualified expenses is subject to taxes and (again, depending on the setup) may also be subject to penalties in addition to the taxes.
This is just a *g*e*n*e*r*a*l* explanation. Different rules apply to different plans and those rules can be affected by what type of business you have, what state you're in and other factors. You'd be best to consult with a tax professional in your local jurisdiction to get the facts as they will apply to your specific situation and setup.
