<prompt> Human: I was working in a co-op for agriculture and agri food Canada over the summer May 5 to August 29 and was not taken off the payroll. I was not paid for the first month of work or thereabouts so I was under the impression that the paychecks I continued to receive into September were to make up for that month. I informed them of the error and they said I will be receiving a letter in the mail to address the issue. What should I do and do I have to pay back that money?  <response>: If the money is not rightfully yours, yes, you have to pay it back. 