Yes, it is legal if there is an union/employment contract or stated employment policy indicating that your employer can charge back errors.  However, even if it can require repayment for this type of loss, your employer cannot simply deduct from your paycheck; payroll deductions are subject to a number of limitations.  In such a case, you might need to make repayment by writing a check, etc. to your employer (as opposed to automatic paycheck withholding).Without a previous agreement requiring repayment, an employer may not force the employee to repay money for a loss.  However, in an "at will" employment situation (and most employment arrangements are), an employer can terminate an employee for not making repayment. The fact is that an at-will employer can fire an employee for any reason or no reason at all.  So trying to prove your point may cost you more (like your job) in the long run.  While unfair, it may just be worth it to let the deduction be made and keep working.Bottom line, you just may want to work out a repayment arrangement to keep the peace - and your job.