some states say after a threshold is reached each day you're a guest AFTER the threshold has been reached is tax exempt, other states say once the threshold is reached ALL nights leading up to, including and after the threshold are tax exempt....others (Mich comes to mind) say if any tax has been incorrectly collected only the STATE may issue the refund....and as noted earlier several states moved to increase the number of days to reach the threshold in the past few years to lower the amount of guests reaching the threshold....oh and my favorite some states say just being registered isn't enough, you must be in the same room for all of the nights and can not move regardless of reason (always fun when a mechnical issue arises)