Deducting leave for partial-day absences

Q. Recently, we audited our jobs and determined that some employees were classified as hourly when they should be exempt. We reclassified them. But now, I have a question about handling time off for our newly exempt employees. By law, are we required to NOT charge an exempt person’s time if they’re out of the office for a half day? And if we do start charging an exempt person’s time (vacation or personal) if they miss an hour or two, are we setting ourselves up to be sued?