if the employer discovered the error in 2025 and paid you renumeration in that year, the reg says the employer can deduct it from your 2025 renumeration. if none was paid, the obligation of the employee to the employer with respect to the undercollection is a matter for settlement between the employee and the employer. the last sentence means you should see a lawyer that specializes in employee compensation issues.
however, when did the employer "ascertain" the error. that too is a question for a lawyer
