How is it legal for an employer to deduct from an employee''s wages because a customer''s check bounced?

In general, in the absence of a specific state law to the contrary, an employer and employee are free to agree on any basis of compensation for the employee. For example, the employee may be paid on a commission basis depending on the sales he generates, and if one of those customers is dissatisfied and returns the goods for a refund, the employer may lawfully reverse the commission payment. Under federal law, the net pay to the employee may not be less than the mininum wage. A few states have state laws that expressly prohibit an employer from making deductions from employees' wages for, for example, breakage. You should consult with an attorney to determine whether the specific facts of your situation have resulted in a permissible deduction.