Legal Question in Employment Law in California

Ordinarily, an employer cannot collect a debt out of a paycheck without the employee's agreement in writing, and only then if the result would not impair the employee's basic earnings needed to meet usual living expenses. Statutes address this question. See Labor Code Sections 221, 222, and 300. Look also at the case of Barnhill vs. Robert Sanders & Co. (1981) 125 Cal.App.3d 1. An employer has no right of "set-off" of a wage obligation for an employee debt.

But you describe a situation different that raw exercise of "off-set" by an over-reaching employer. You refer to a signed written consent by the employee. An non-coerced agreement in writing would simply be an agreement to the form of payment, and would be legal.

Bonus information: An inadvertent excess pay rate made to the employee may also be deducted. California's DLSE opinion letters allow this deduction. However, the wise employer, and the smart employee, should work out a reimbursement plan in writing signed by both parties as protection of each.