In most cases, to be eligible for federal financial aid, you must be enrolled at least half time. If you are an undergraduate student, half time is usually define as between 6 and 8 credits. So, if you were at 8 credits and you drop 4, that would put you below half time, and you would not be eligible for aid. this rule only affects federal aid (FAFSA), but often eligibility for state and institutional aid is also determined by eligibility for federal aid. However, there are exceptions, so you would need to speak with a financial aid counselor at your school to determine what would happen in your particular case.