Unless you specifically agreed to such a deduction in writng, then it is illegal. An employee must be paid for all time worked. That having been said, your employer may have the right to charge you for any oustanding Iccounts receivable (depending on specific state law). if so, then you can either agree to pay any such amounts or your employer could even sue in small claims court for reimbursement. At this point you may want to put a call into a local attorney to be certain of your rights.