From the SEPE website:
When any situation occurs that involves the loss or interruption of the collection of an unemployment benefit or subsidy (for example, a placement or transfer abroad), you must notify the employment office.
In these cases, it corresponds to collect the benefit until the day prior to the day on which the cause that interrupted the payment has occurred.
If the benefit has been collected or has been credited to your bank account for an amount greater than that which corresponds to it or for a period of time that it should not have been received, the Public State Employment Service (SEPE) will notify you, informing you of the reason of the improper collection, the amount you owe and will indicate an account number where to make the return.
You can report the situation that causes your ‘baja’ from the benefits (placement, retirement …) to SEPE:
Through the Internet, at www.sepe.es, if you have a digital certificate, electronic ID or Cl@ve username and password.
Calling the citizen service telephone number.
At the employment office in your area, upon request for an appointment on the aforementioned website. (includes COVID info).