Typically the Revenue Officer will make his or her decision based upon information provided at a 4180 interview. Other evidence may include a bank signature card or paychecks with your client’s signature on the signatory line. This could have been provided by your client or another person that worked for the company for which your Client worked. Once the assessment becomes final, you should be sent paperwork stating on what basis your client was assessed. If you disagree, you have 60 days to appeal the assessment.