It is not uncommon for a defendant to overpay permanent disability (PD) benefits. An overpayment might occur for several reasons. The defendant might not receive the physician's report declaring the applicant permanent and stationary until long after the evaluation. Or a defendant simply might make a mistake and pay more PD than required.
Labor Code § 4909 states, "Any payment, allowance, or benefit received by the injured employee ... [that] was not then due and payable ... shall not, in the absence of any agreement, be an admission of liability for compensation on the part of the employer, but any such payment, allowance, or benefit may be taken into account by the appeals board in fixing the amount of the compensation to be paid." LC 4909 is widely understood as empowering the Workers' Compensation Appeals Board (WCAB) with discretion to grant or deny credit for overpayments.